Fusion-formable glass-based articles including a metal oxide concentration gradient

ABSTRACT

A glass-based article including a first surface and a second surface opposing the first surface defining a thickness (t) of about 3 millimeters or less (e.g., about 1 millimeter or less), and a stress profile, wherein all points of the stress profile between a thickness range from about 0·t up to 0.3·t and from greater than about 0.7·t to t, comprise a tangent with a slope having an absolute value greater than about 0.1 MPa/micrometer. In some embodiments, the glass-based article includes a non-zero metal oxide concentration that varies along at least a portion of the thickness (e.g., 0·t to about 0.3·t) and a maximum central tension of less than about 71.5/√(t) (MPa). In some embodiments, the concentration of metal oxide or alkali metal oxide decreases from the first surface to a point between the first surface and the second surface and increases from the point to the second surface. The concentration of the metal oxide may be about 0.05 mol % or greater or about 0.5 mol % or greater throughout the thickness. Methods for forming such glass-based articles are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofProvisional Application Ser. No. 62/365,534 filed on Jul. 22, 2016, U.S.Provisional Application Ser. No. 62/364,687 filed on Jul. 20, 2016, U.S.Provisional Application Ser. No. 62/320,095 filed on Apr. 8, 2016 andU.S. Provisional Application Ser. No. 62/266,411 filed on Dec. 11, 2015,the contents of each of which are relied upon and incorporated herein byreference in their entireties.

BACKGROUND

This disclosure relates to fusion-formable, glass-based articlesexhibiting improved damage resistance, including improved fractureresistance, and more particularly to fusion-formable, glass and glassceramic articles exhibiting a non-zero metal oxide concentrationgradient or concentration that varies along a substantial portion of thethickness.

Glass-based articles often experience severe impacts that can introducelarge flaws into a surface of such articles. Such flaws can extend todepths of up to about 200 micrometers (microns, or μm) from the surface.Traditionally, thermally tempered glass has been used to preventfailures caused by the introduction of such flaws into the glass becausethermally tempered glass often exhibits large compressive stress (CS)layers (e.g., approximately 21% of the total thickness of the glass),which can prevent the flaws from propagating further into the glass andthus, can prevent failure. An example of a stress profile generated bythermal tempering is shown in FIG. 1. In FIG. 1, the thermally treatedglass article 100 includes a first surface 101, a thickness t₁, and asurface CS 110. The thermally treated glass article 100 exhibits a CSthat decreases from the first surface 101 to a depth of compression 130,as defined herein, at which depth the stress changes from compressive totensile stress and reaches a maximum central tension (CT) 120.

Thermal tempering is currently limited to thick glass-based articles(i.e., glass-based articles having a thickness t₁ of about 3 millimetersor greater) because, to achieve the thermal strengthening and thedesired residual stresses, a sufficient thermal gradient must be formedbetween the core of such articles and the surface. Such thick articlesare undesirable or not practical in many applications such as display(e.g., consumer electronics, including mobile phones, tablets,computers, navigation systems, and the like), architecture (e.g.,windows, shower panels, countertops etc.), transportation (e.g.,automotive, trains, aircraft, sea craft, etc.), appliance, or anyapplication that requires superior fracture resistance but thin andlight-weight articles.

Although chemical strengthening is not limited by the thickness of theglass-based article in the same manner as thermally tempering, knownchemically strengthened glass-based articles do not exhibit the stressprofile of thermally tempered glass-based articles. An example of astress profile generated by chemical strengthening (e.g., by an ionexchange process), is shown in FIG. 2. In FIG. 2, the chemicallystrengthened glass-based article 200 includes a first surface 201, athickness t₂ and a surface CS 210. The glass-based article 200 exhibitsa CS that decreases from the first surface 201 to a DOC 230, as definedherein, at which depth the stress changes from compressive to tensilestress and reaches a maximum CT 220. As shown in FIG. 2, such profilesexhibit a substantially flat CT region or CT region with a constant ornear constant tensile stress along at least a portion of the CT region.Often, known chemically strengthened glass-based articles exhibit alower maximum CT value, as compared to the maximum central value shownin FIG. 1.

Accordingly, there is a need for thin glass-based articles that exhibitimproved fracture resistance.

SUMMARY

A first aspect of this disclosure pertains to a glass-based articleincluding a first surface and a second surface opposing the firstsurface defining a thickness (t) in millimeters (mm), a concentration ofa metal oxide that is both non-zero and varies along a thickness rangefrom about 0·t to about 0.3·t; and a central tension (CT) regioncomprising a maximum CT of less than about 71.5/√(t) (MPa). In one ormore embodiments, the when the glass-based article is fractured, theglass-based article fractures into at most 2 fragments/inch² as measuredby the “Frangibility Test”, as described Z. Tang, et al. AutomatedApparatus for Measuring the Frangibility and Fragmentation ofStrengthened Glass. Experimental Mechanics (2014) 54:903-912. The numberof fragments is divided by the area of the sample being tested (insquare inches), and the sample size used was a 5 cm by 5 cm (2 inch by 2inch) square.

In one or more embodiments, the concentration of the metal oxide isnon-zero and varies along the entire thickness. In one or moreembodiments, the metal oxide generates a stress along the thicknessrange. The monovalent ion of the metal oxide may have the largest ionicdiameter of all of the monovalent ions of the metal oxides in theglass-based substrate. The concentration of the metal oxide may decreasefrom the first surface to a point between the first surface and thesecond surface and increases from the point to the second surface. Forexample, the concentration of the metal oxide at the first surface maybe about 1.5 (or more) times greater than the concentration of the metaloxides at a depth equal to about 0.5·t. In some instances, theconcentration of the metal oxide is about 0.05 mol % or greaterthroughout the thickness (e.g., in the range from about 1 mol % to about15 mol %). In some instances, the concentration of the metal oxide maydecrease from the first surface to a value at a point between the firstsurface and the second surface and increase from the value to the secondsurface. The metal oxide may include any one or more of Li₂O, Na₂O, K₂O,Rb₂O, and Cs₂O. In one or more embodiments, the metal oxideconcentration gradient may be present in the CT region of theglass-based article.

In one or more embodiments, the glass-based article includes a stressprofile extending along the thickness, wherein all points of the stressprofile between a thickness range from about 0·t up to 0.3·t and fromgreater than about 0.7·t to t, comprise a tangent having a slope with anabsolute value of greater than about 0.1 MPa/micrometer (i.e., a tangenthaving a slope with a value that is less than about −0.1 MPa/micrometeror greater than about 0.1 MPa/micrometer). In some embodiments, thetangent may be described and used interchangeably with “local gradient”,which is defined as the change in stress magnitude as a function ofdepth, as the depth increment approaches zero. In some embodiments, thestress profile comprises a maximum CS, a DOC and a maximum CT of lessthan about 71.5/√(t) (MPa), wherein the ratio of maximum CT to absolutevalue of maximum CS is in the range from about 0.01 to about 0.2 andwherein the DOC is about 0.1·t or greater.

In one or more embodiments, the glass-based articles described hereinexhibit certain fracture behavior. For example, in one or moreembodiments, when the glass-based article is fractured by a single event(i.e., a single impact such as being dropped or being impacted once withan implement), the glass-based article fractures into at most 2fragments/inch², wherein the sample size used was a 5 cm by 5 cm (2 inchby 2 inch) square.

The glass-based article of one or more embodiments may include a surfacecompressive stress (CS) of about 300 MPa or greater, or about 400 MPa orgreater. In some embodiments, the glass-based article includes a surfaceCS of about 200 MPa or greater and a chemical depth of layer of about0.4·t or greater. In one or more embodiments, the CS may extend from thefirst surface to a DOC, wherein the DOC is about 0.1·t or greater. Theglass-based article of some embodiments exhibits a ratio of maximum CTto absolute value of surface CS (which may include the maximum CS) inthe range from about 0.01 to about 0.2. Optionally, the surface CS isgreater than the maximum CT.

In one or more embodiments, the glass-based article includes a firstmetal oxide concentration and a second metal oxide concentration,wherein the first metal oxide concentration is in the range from about 0mol % to about 15 mol % from a first thickness range from about 0·t toabout 0.5·t, and wherein the second metal oxide concentration is in therange from about 0 mol % to about 10 mol % from a second thickness rangefrom about 0 micrometers to about 25 micrometers. Optionally, theglass-based article includes a third metal oxide.

In one or more embodiments, the glass-based article includes aconcentration of a metal oxide that is both non-zero and varies along athickness range from about 0·t to about 0.3·t (or from about 0·t toabout 0.4·t or from about 0·t to about 0.45·t), a surface compressivestress of greater than about 200 MPa or greater; and a CT region havinga maximum CT of less than about 71.5/√(t) (MPa), wherein “71.5” is inunits of MPa·(mm)̂̂0.5, and “t” is in millimeters (mm).

The glass-based article may have a thickness t of about 3 millimeters orless or about 1 millimeter or less. The glass-based article may have anamorphous structure, a crystalline structure or a combination of both.The glass-based article may exhibit a transmittance of about 88% orgreater over a wavelength in the range from about 380 nm to about 780nm. Moreover, in some embodiments, the glass-based article may exhibit aCIELAB color space coordinates, under a CIE illuminant F02, of L* valuesof about 88 and greater, a* values in the range from about −3 to about+3, and b* values in the range from about −6 to about +6.

In one or more embodiments, the glass-based article includes a Young'smodulus of less than 80 GPa. The Young's modulus value recited in thisdisclosure refers to a value as measured by a resonant ultrasonicspectroscopy technique of the general type set forth in ASTM E2001-13,titled “Standard Guide for Resonant Ultrasound Spectroscopy for DefectDetection in Both Metallic and Non-metallic Parts.” The glass-basedarticle includes a liquidus viscosity of about 100 kilopoise (kP) orgreater.

The glass-based article may include a composition having any one or moreof: a composition comprising a combined amount of Al₂O₃ and Na₂O ofgreater than about 15 mol %, a composition comprising greater than about4 mol % Na₂O, a composition substantially free of B₂O₃, ZnO, or bothB₂O₃ and ZnO, and a composition comprising a non-zero amount of P₂O₅.

The glass-based article may include a monovalent ion (e.g., sodium ionor potassium ion) diffusivity of about 450 μm²/hour or greater at about460° C. In one or more embodiments, this monovalent ion diffusivity isexhibited in combination with and a DOC greater than about 0.15·t, andwherein the surface CS is 1.5 times the maximum CT or greater.

In some embodiments, the glass-based article comprises a fracturetoughness (K_(1C)) of about 0.7 MPa·m^(1/2) or greater.

In one or more embodiments, the glass-based article exhibits a storedtensile energy of about greater than 0 J/m2 to less than 40 J/m².

In one or more embodiments, the glass-based article includes a stressprofile including a CS region and a CT region, wherein the CT region isapproximated by the equationStress(x)=MaxT−(((CT_(n)·(n+1))/0.5n)·|(x/t)−0.5|n), wherein MaxT is amaximum tension value, CT_(n) is less than or equal to MaxT and is apositive value in units of MPa, x is position along the thickness (t) inmicrometers, and n is in the range from 1.5 to 5 (or from 1.5 to 2). Insome embodiments, the CT region comprises a maximum CT value in therange from about 50 MPa to about 250 MPa and the maximum CT value is ata depth in the range from about 0.4t to about 0.6t. In some instances,from a thickness in the range from about 0t to about 0.1t, the stressprofile comprises a slope whose magnitude (in absolute value) is in therange from about 20 MPa/micron to about 200 MPa/micron. In one or moreembodiments, the stress profile is approximated by a combination of aplurality of error functions as measured from 0.5t to the surface.

A second aspect of this disclosure pertains to the use of a glasscomposition in a strengthened glass-based article, comprising (in mol%): SiO₂ in an amount in the range from about 60 to about 75, Al₂O₃ inan amount in the range from about 12 to about 20, B₂O₃ in an amount inthe range from about 0 to about 5, Li₂O in an amount in the range fromabout 2 to about 8, Na₂O in an amount greater than 4, P₂O₅ in a non-zeroamount, MgO in an amount in the range from about 0 to about 5, ZnO in anamount in the range from about 0 to about 3, CaO in an amount in therange from about 0 to about 5, wherein the glass composition ision-exchangeable and is amorphous, wherein the total amount of Al₂O₃ andNa₂O is greater than about 15 mol %, wherein the glass composition issubstantially free of nucleating agents, and wherein the glasscomposition comprises a liquidus viscosity of about 100 kP or greater.In one or more embodiments, the glass composition is substantially freeof B₂O₃, ZnO, or both B₂O₃ and ZnO.

A third aspect of this disclosure pertains to a glass substratecomprising a composition including, in mol %, SiO₂ in an amount in therange from about 60 to about 75, Al₂O₃ in an amount in the range fromabout 12 to about 20, B₂O₃ in an amount in the range from about 0 toabout 5, Li₂O in an amount in the range from about 2 to about 8, Na₂O inan amount greater than about 4, MgO in an amount in the range from about0 to about 5, ZnO in an amount in the range from about 0 to about 3, CaOin an amount in the range from about 0 to about 5, and P₂O₅ in anon-zero amount; wherein the glass substrate is ion-exchangeable and isamorphous, wherein total amount of Al₂O₃ and Na₂O in the composition isgreater than about 15 mol %, wherein the glass composition issubstantially free of nucleating agents and comprises a liquidusviscosity of about 100 kP or greater.

In some embodiments, the glass substrate is amorphous and isstrengthened, wherein the Na₂O concentration varies, wherein thecomposition is substantially free of nucleating agents, total amount ofAl₂O₃ and Na₂O in the composition is greater than about 15 mol %,wherein the glass composition is substantially free of nucleatingagents, and comprises a liquidus viscosity of about 100 kP or greater.In some embodiments the glass substrate includes a non-zero amount ofP₂O₅.

A fourth aspect of this disclosure pertains to a device comprising: ahousing having front, back, and side surfaces; electrical componentsthat are at least partially inside the housing; a display at or adjacentto the front surface of the housing; and a cover substrate disposed overthe display, wherein the cover substrate comprises a glass-based articleaccording the embodiments described herein.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view across a thickness of a known,thermally tempered glass article;

FIG. 2 is a cross-sectional view across a thickness of a known,chemically strengthened glass article;

FIG. 3 is a cross-sectional view across a thickness of a chemicallystrengthened glass-based article according to one or more embodiments ofthis disclosure;

FIG. 4 is a graph illustrating various stress profiles according to oneor more embodiments of this disclosure;

FIGS. 5A-5B are graphs showing the maximum tensile stress (MPa) as afunction of normal load (N) applied to a surface of a glass-basedarticle according to one or more embodiments;

FIG. 6 is a is a schematic cross-sectional view of a ring-on-ringapparatus;

FIG. 7 is a schematic cross-sectional view of an embodiment of theapparatus that is used to perform the inverted ball on sandpaper (IBoS)test described in the present disclosure;

FIG. 8 is a schematic cross-sectional representation of the dominantmechanism for failure due to damage introduction plus bending thattypically occurs in glass-based articles that are used in mobile or handheld electronic devices;

FIG. 9 is a flow chart for a method of conducting the IBoS test in theapparatus described herein;

FIG. 10 is a graph showing the maximum CT values for Examples 1A-1G as afunction of ion exchange time;

FIG. 11 is a graph showing the measured stress of Example 1E as afunction of depth extending from the surface of the glass-based articleof Example 1E into the glass-based article;

FIG. 12 is a graph showing the load to failure values for glass-basedarticles according to Example 2A after being abraded at different loadsor pressures;

FIG. 13 is a graph showing the heights at which the glass-based articlesaccording to Example 2A failed after being dropped onto 180 gritsandpaper and then onto 30 grit sandpaper;

FIG. 14 is a graph showing the heights at which the glass-based articlesaccording to Example 3A and Comparative Example 3B failed after beingdropped onto 30 grit sandpaper;

FIG. 15 is a graph comparing the average load to failure of glass-basedarticles according to Example 3A and Comparative Example 3B, after beingabraded at a load or pressure of 25 psi;

FIG. 16 is a graph comparing the average load to failure of glass-basedarticles according to Example 3A and Comparative Example 3B, after beingabraded at a load or pressure of 45 psi;

FIG. 17 is a graph showing the stress profiles of Examples 4A-1 through4A-6 as a function of depth;

FIG. 18 is a graph showing the maximum CT and DOC values of Examples4A-1 through 4A-6 as a function of ion exchange time;

FIG. 19 is a graph showing the stress profiles of Examples 4B-1 through4B-6 as a function of depth;

FIG. 20 is a graph showing the maximum CT and DOC values of Examples4B-1 through 4B-6 as a function of ion exchange time;

FIG. 21 is a graph showing the stress profiles of Examples 4C-1 through4C-6 as a function of depth;

FIG. 22 is a graph showing the maximum CT and DOC values of Examples4C-1 through 4C-6 as a function of ion exchange time;

FIG. 23 is a graph showing the stress profiles of Examples 4D-1 through4D-6 as a function of depth;

FIG. 24 is a graph showing the maximum CT and DOC values of Examples4D-1 through 4D-6 as a function of ion exchange time;

FIG. 25 is a graph showing the stress profiles of Comparative Example 5Aand Example 5B as a function of depth;

FIG. 26 is a graph showing the stored tensile energy of ComparativeExample 5A and Example 5B as a function of maximum CT;

FIG. 27 is a graph showing stored tensile energy of Comparative Example5C and Example 5D as a function of maximum CT;

FIG. 28 is a front plan view of an electronic device incorporating oneor more embodiments of the glass-based articles described herein.

FIG. 29 is a side view of a testing apparatus for glass-based articles;

FIG. 30 is a side view of a portion of the testing apparatus shown inFIG. 29;

FIG. 31 is a rear perspective view of the testing apparatus shown inFIG. 29;

FIG. 32 is a front perspective view of the testing apparatus shown inFIG. 29;

FIG. 33 is side view of a testing apparatus for glass-based articles;

FIG. 34 is a side view of a portion of the testing apparatus shown inFIG. 29;

FIG. 35 is a graph of average impact force versus swing angle dataobtained on the testing apparatus shown in FIG. 29 for various glasssamples;

FIG. 36 is a bar graph of mean impact position data obtained on thetesting apparatus shown in FIG. 29 for various glass samples; and

FIG. 37 is a graph showing retained strength values for various samples

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying examples and drawings.

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range as well as any ranges therebetween. As usedherein, the indefinite articles “a,” “an,” and the correspondingdefinite article “the” mean “at least one” or “one or more,” unlessotherwise specified. It also is understood that the various featuresdisclosed in the specification and the drawings can be used in any andall combinations.

As used herein, the terms “glass-based article” and “glass-basedsubstrates” are used in their broadest sense to include any object madewholly or partly of glass. Glass-based articles include laminates ofglass and non-glass materials, laminates of glass and crystallinematerials, and glass-ceramics (including an amorphous phase and acrystalline phase). Unless otherwise specified, all compositions areexpressed in terms of mole percent (mol %).

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

Unless otherwise specified, all temperatures are expressed in terms ofdegrees Celsius (° C.). As used herein the term “softening point” refersto the temperature at which the viscosity of a glass is approximately10^(7.6) poise (P), the term “anneal point” refers to the temperature atwhich the viscosity of a glass is approximately 10^(13.2) poise, theterm “200 poise temperature (T^(200P))” refers to the temperature atwhich the viscosity of a glass is approximately 200 poise, the term“10¹¹ poise temperature” refers to the temperature at which theviscosity of a glass is approximately 10¹¹ poise, the term “35 kPtemperature (T^(35kP))” refers to the temperature at which the viscosityof a glass is approximately 35 kilopoise (kP), and the term “160 kPtemperature (T^(160kP))” refers to the temperature at which theviscosity of a glass is approximately 160 kP.

Referring to the drawings in general and to FIGS. 1-3 in particular, itwill be understood that the illustrations are for the purpose ofdescribing particular embodiments and are not intended to limit thedisclosure or appended claims thereto. The drawings are not necessarilyto scale, and certain features and certain views of the drawings may beshown exaggerated in scale or in schematic in the interest of clarityand conciseness.

As used herein, DOC refers to the depth at which the stress within theglass-based article changes compressive to tensile stress. At the DOC,the stress crosses from a positive (compressive) stress to a negative(tensile) stress (e.g., 130 in FIG. 1) and thus exhibits a stress valueof zero.

As used herein, the terms “chemical depth”, “chemical depth of layer”and “depth of chemical layer” may be used interchangeably and refer tothe depth at which an ion of the metal oxide or alkali metal oxide(e.g., the metal ion or alkali metal ion) diffuses into the glass-basedarticle and the depth at which the concentration of the ion reaches aminimum value, as determined by Electron Probe Micro-Analysis (EPMA) orGlow Discharge-Optical Emission Spectroscopy (GD-OES)). In particular,to assess the depth of Na₂O diffusion or Na+ ion concentration may bedetermined using EPMA and a surface stress meter (described in moredetail below).

According to the convention normally used in the art, compression isexpressed as a negative (<0) stress and tension is expressed as apositive (>0) stress, unless specifically noted otherwise. Throughoutthis description, however, when speaking in terms of compressive stressCS, such is given without regard to positive or negative values—i.e., asrecited herein, CS=|CS|.

Described herein are thin, chemically strengthened glass-based articlesthat include glasses, such as silicate glasses includingalkali-containing glass, and glass-ceramics that may be used as a coverglass for mobile electronic devices and touch-enabled displays. Theglass-based articles may also be used in displays (or as displayarticles) (e.g., billboards, point of sale systems, computers,navigation systems, and the like), architectural articles (walls,fixtures, panels, windows, etc.), transportation articles (e.g., inautomotive applications, trains, aircraft, sea craft, etc.), appliances(e.g., washers, dryers, dishwashers, refrigerators and the like), or anyarticle that requires some fracture resistance.

In particular, the glass-based articles described herein are thin andexhibit stress profiles that are typically only achievable throughtempering thick glass articles (e.g., having a thickness of about 2 mmor 3 mm or greater). The glass-based articles exhibit unique stressprofiles along the thickness thereof. In some cases, the glass-basedarticles described herein exhibit a greater surface CS than temperedglass articles. In one or more embodiments, the glass-based articleshave a compressive stress layer that extends deeper into the glass-basedarticle (in which the CS decreases and increases more gradually thanknown chemically strengthened glass-based articles) such the glass-basedarticle exhibits substantially improved fracture resistance, even whenthe glass-based article or a device including the same is dropped on ahard surface (e.g., granite) or a hard and rough surface (e.g.,asphalt). The glass-based articles of one or more embodiments exhibit agreater maximum CT value than some known chemically strengthened glasssubstrates.

CS and depth of penetration of potassium ions (“Potassium DOL”) aremeasured using those means known in the art. Potassium DOL isdistinguished from DOC because it represents the depth of potassiumpenetration as a result of an ion exchange process. Potassium DOL istypically less than the DOC for the articles described herein. CS andPotassium DOL are measured by surface stress meter (FSM) usingcommercially available instruments such as the FSM-6000, manufactured byOrihara Industrial Co., Ltd. (Japan). Surface stress measurements relyupon the accurate measurement of the stress optical coefficient (SOC),which is related to the birefringence of the glass. SOC in turn ismeasured according to a modified version of Procedure C described inASTM standard C770-98 (2013), entitled “Standard Test Method forMeasurement of Glass Stress-Optical Coefficient,” the contents of whichare incorporated herein by reference in their entirety. The modificationincludes using a glass disc as the specimen with a thickness of 5 to 10mm and a diameter of 12.7 mm, wherein the disc is isotropic andhomogeneous and core drilled with both faces polished and parallel. Themodification also includes calculating the maximum force, Fmax to beapplied. The force should be sufficient to produce 20 MPa or morecompression stress. Fmax is calculated as follows:

Fmax=7.854*D*h

Where:

Fmax=Force in Newtons

D=the diameter of the disc

h=the thickness of the light path

For each force applied, the stress is computed as follows:

σ_(MPa)=8F/(π*D*h)

Where:

F=Force in Newtons

D=the diameter of the disc

h=the thickness of the light path

DOC and maximum CT values are measured using a scattered lightpolariscope (SCALP). Refracted near-field (RNF) method or SCALP may beused to measure the stress profile. When the RNF method is utilized, themaximum CT value provided by SCALP is utilized. In particular, thestress profile measured by the RNF method is force balanced andcalibrated to the maximum CT value provided by a SCALP measurement. TheRNF method is described in U.S. Pat. No. 8,854,623, entitled “Systemsand methods for measuring a profile characteristic of a glass sample”,which is incorporated herein by reference in its entirety. Inparticular, the RNF method includes placing the glass-based articleadjacent to a reference block, generating a polarization-switched lightbeam that is switched between orthogonal polarizations at a rate ofbetween 1 Hz and 50 Hz, measuring an amount of power in thepolarization-switched light beam and generating a polarization-switchedreference signal, wherein the measured amounts of power in each of theorthogonal polarizations are within 50% of each other. The methodfurther includes transmitting the polarization-switched light beamthrough the glass sample and reference block for different depths intothe glass sample, then relaying the transmitted polarization-switchedlight beam to a signal photodetector using a relay optical system, withthe signal photodetector generating a polarization-switched detectorsignal. The method also includes dividing the detector signal by thereference signal to form a normalized detector signal and determiningthe profile characteristic of the glass sample from the normalizeddetector signal. The RNF profile is then smoothed, and used for the CTregion. As noted above, the FSM technique is used for the surface CS andslope of the stress profile in the CS region near the surface.

As stated above, the glass-based articles described herein arechemically strengthened by ion exchange and exhibit stress profiles thatare distinguished from those exhibited by known strengthened glassarticles. In this disclosure glass-based substrates are generallyunstrengthened and glass-based articles generally refer to glass-basedsubstrates that have been strengthened (by, for example, ion exchange).In this process, ions at or near the surface of the glass-based articleare replaced by—or exchanged with—larger ions having the same valence oroxidation state. In those embodiments in which the glass-based articlecomprises an alkali aluminosilicate glass, ions in the surface layer ofthe glass and the larger ions are monovalent alkali metal cations, suchas Li⁺ (when present in the glass-based article), Na⁺, K⁺, Rb⁺, and Cs⁺.Alternatively, monovalent cations in the surface layer may be replacedwith monovalent cations other than alkali metal cations, such as Ag⁺ orthe like. In such embodiments, the monovalent ions (or cations)exchanged into the glass-based substrate generate a stress in theresulting glass-based article.

Ion exchange processes are typically carried out by immersing aglass-based substrate in a molten salt bath (or two or more molten saltbaths) containing the larger ions to be exchanged with the smaller ionsin the glass-based substrate. It should be noted that aqueous salt bathsmay also be utilized. In addition, the composition of the bath(s) mayinclude more than one type of larger ion (e.g., Na+ and K+) or a singlelarger ion. It will be appreciated by those skilled in the art thatparameters for the ion exchange process, including, but not limited to,bath composition and temperature, immersion time, the number ofimmersions of the glass-based article in a salt bath (or baths), use ofmultiple salt baths, additional steps such as annealing, washing, andthe like, are generally determined by the composition of the glass-basedarticle (including the structure of the article and any crystallinephases present) and the desired DOC and CS of the glass-based articlethat results from strengthening. By way of example, ion exchange ofglass-based substrates may be achieved by immersion of the glass-basedsubstrates in at least one molten bath containing a salt such as, butnot limited to, nitrates, sulfates, and chlorides of the larger alkalimetal ion. Typical nitrates include KNO₃, NaNO₃, LiNO₃, NaSO₄ andcombinations thereof. The temperature of the molten salt bath typicallyis in a range from about 380° C. up to about 450° C., while immersiontimes range from about 15 minutes up to about 100 hours depending onglass thickness, bath temperature and glass (or monovalent ion)diffusivity. However, temperatures and immersion times different fromthose described above may also be used.

In one or more embodiments, the glass-based substrates may be immersedin a molten salt bath of 100% NaNO₃ having a temperature from about 370°C. to about 480° C. In some embodiments, the glass-based substrate maybe immersed in a molten mixed salt bath including from about 5% to about90% KNO₃ and from about 10% to about 95% NaNO₃. In some embodiments, theglass-based substrate may be immersed in a molten mixed salt bathincluding Na₂SO₄ and NaNO₃ and have a wider temperature range (e.g., upto about 500° C.). In one or more embodiments, the glass-based articlemay be immersed in a second bath, after immersion in a first bath.Immersion in a second bath may include immersion in a molten salt bathincluding 100% KNO₃ for 15 minutes to 8 hours.

In one or more embodiments, the glass-based substrate may be immersed ina molten, mixed salt bath including NaNO₃ and KNO₃ (e.g., 49%/51%,50%/50%, 51%/49%) having a temperature less than about 420° C. (e.g.,about 400° C. or about 380° C.) for less than about 5 hours, or evenabout 4 hours or less.

Ion exchange conditions can be tailored to provide a “spike” or toincrease the slope of the stress profile at or near the surface of theresulting glass-based article. This spike can be achieved by single bathor multiple baths, with the bath(s) having a single composition or mixedcomposition, due to the unique properties of the glass compositions usedin the glass-based articles described herein.

As illustrated in FIG. 3, the glass-based article 300 of one or moreembodiments includes a first surface 302 and a second surface 304opposing the first surface, defining a thickness t. In one or moreembodiments, the thickness t may be about 3 millimeters or less (e.g.,in the range from about 0.01 millimeter to about 3 millimeters, fromabout 0.1 millimeter to about 3 millimeters, from about 0.2 millimeterto about 3 millimeters, from about 0.3 millimeter to about 3millimeters, from about 0.4 millimeter to about 3 millimeters, fromabout 0.01 millimeter to about 2.5 millimeters, from about 0.01millimeter to about 2 millimeters, from about 0.01 millimeter to about1.5 millimeters, from about 0.01 millimeter to about 1 millimeter, fromabout 0.01 millimeter to about 0.9 millimeter, from about 0.01millimeter to about 0.8 millimeter, from about 0.01 millimeter to about0.7 millimeter, from about 0.01 millimeter to about 0.6 millimeter, fromabout 0.01 millimeter to about 0.5 millimeter, from about 0.1 millimeterto about 0.5 millimeter, or from about 0.3 millimeter to about 0.5millimeter.)

The glass-based article includes a stress profile that extends from thefirst surface 302 to the second surface 304 (or along the entire lengthof the thickness t). In the embodiment shown in FIG. 3, the stressprofile 312 as measured by SCALP or RNF as described herein isillustrated. The y-axis represents the stress value and the x-axisrepresents the thickness or depth within the glass-based article.

As illustrated in FIG. 3, the stress profile 312 includes a CS layer 315(with a surface CS 310), a CT layer 325 (with a maximum CT 320) and aDOC 330 at which the stress profile 312 turns from compressive totensile. The CS layer has an associated depth or length 317 extendingfrom a surface 302, 304 to the DOC 330. The CT layer 325 also has anassociated depth or length 327 (CT region or layer).

The surface CS 310 may be about 150 MPa or greater or about 200 MPa orgreater (e.g., about 250 MPa or greater, about 300 MPa or greater, about400 MPa or greater, about 450 MPa or greater, about 500 MPa or greater,or about 550 MPa or greater). The surface CS 310 may be up to about 900MPa, up to about 1000 MPa, up to about 1100 MPa, or up to about 1200MPa. The surface CS values herein may also comprise the maximum CS. Insome embodiments, the surface CS is less than the maximum CS.

The maximum CT 320 may be less than about 71.5/√t), where t is thicknessis mm. In one or more embodiments, the maximum CT 320 may be greaterthan about 45/√(t). In one or more embodiments, the maximum CT may beabout 80 MPa or less, about 75 MPa or less, or about 70 MPa or less(e.g., about 60 MPa or less, about 55 MPa or less, 50 MPa or less, orabout 40 MPa or less). In one or more embodiments, the lower limit ofthe maximum CT may be 25 MPa, 40 MPa or 50 MPa. In some embodiments, themaximum CT 320 may be in the range from about 25 MPa to about 80 MPa(e.g., from about 25 MPa to about 75 MPa, from about 25 MPa to about 70MPa, from about 25 MPa to about 65 MPa, from about 40 MPa to about 80MPa, from about 40 MPa to about 75 MPa, from about 40 MPa to about 70MPa, from about 40 MPa to about 65 MPa, from about 45 MPa to about 80MPa, from about 50 MPa to about 80 MPa, or from about 60 MPa to about 80MPa).

The maximum CT 320 may be positioned at a range from about 0.3·t toabout 0.7·t, from about 0.4·t to about 0.6·t or from about 0.45·t toabout 0.55·t. It should be noted that any one or more of surface CS 310and maximum CT 320 may be dependent on the thickness of the glass-basedarticle. For example, glass-based articles having at thickness of about0.8 mm may have a maximum CT of about 75 MPa or less. When the thicknessof the glass-based article decreases, the maximum CT may increase. Inother words, the maximum CT increases with decreasing thickness (or asthe glass-based article becomes thinner).

In some embodiments, the ratio of the maximum CT 320 to the absolutevalue of surface CS 310 is in the range from about 0.01 to about 0.2(e.g., in the range from about 0.01 to about 0.18, from about 0.01 toabout 0.16, from about 0.01 to about 0.15, from about 0.01 to about0.14, from about 0.01 to about 0.1, from about 0.02 to about 0.2, fromabout 0.04 to about 0.2, from about 0.05 to about 0.2, from about 0.06to about 0.2, from about 0.08 to about 0.2, from about 0.1 to about 0.2,or from about 0.12 to about 0.2). In some embodiments, surface CS may be1.5 times (or 2 times or 2.5 times) the maximum CT or greater. In someembodiments, the surface CS may be up to about 48 times the maximum CT,up to 40 times the maximum CT, up to 20 times the maximum CT, 10 up totimes the maximum CT, or up to 8 times the maximum CT. The surface CSmay be in the range from about 5 times up to about 50 times the maximumCT.

In one or more embodiments, the stress profile 312 comprises a maximumCS, which is typically the surface CS 310 and can be found at one orboth of the first surface 302 and the second surface 304. In one or moreembodiments, the CS layer or region 315 extends along a portion of thethickness 317 to the DOC 330 and a maximum CT 320. In one or moreembodiments, the DOC 330 may be about 0.1·t or greater. For example, theDOC 330 may be about 0.12·t or greater, about 0.14·t or greater, about0.15·t or greater, about 0.16·t or greater, 0.17·t or greater, 0.18·t orgreater, 0.19·t or greater, 0.20·t or greater, about 0.21·t or greater,or up to about 0.25·t. In some embodiments, the DOC 330 is less than thechemical depth. The chemical depth may be about 0.4·t or greater, 0.5·tor greater, about 0.55·t or greater, or about 0.6·t or greater.

In one or more embodiments, the glass-based article comprises apotassium DOL in the range from about 6 micrometers to about 20micrometers. In some embodiments, the potassium DOL may be expressed asa function of the thickness t of the glass-based article. In one or moreembodiments, potassium DOL may be in the range from about 0.005t toabout 0.05t. In some embodiments, the potassium DOL may be in the rangefrom about 0.005t to about 0.05t, from about 0.005t to about 0.045t,from about 0.005t to about 0.04t, from about 0.005t to about 0.035t,from about 0.005t to about 0.03t, from about 0.005t to about 0.025t,from about 0.005t to about 0.02t, from about 0.005t to about 0.015t,from about 0.005t to about 0.01t, from about 0.006t to about 0.05t, fromabout 0.008t to about 0.05t, from about 0.01t to about 0.05t, from about0.015t to about 0.05t, from about 0.02t to about 0.05t, from about0.025t to about 0.05t, from about 0.03t to about 0.05t, or from about0.01t to about 0.02t.

In one or more embodiments, the compressive stress value at thepotassium DOL depth may be in the range from about 50 MPa to about 300MPa. In some embodiments, the compressive stress value at the potassiumDOL depth may be in the range from about 50 MPa to about 280 MPa, fromabout 50 MPa to about 260 MPa, from about 50 MPa to about 250 MPa, fromabout 50 MPa to about 240 MPa, from about 50 MPa to about 220 MPa, fromabout 50 MPa to about 200 MPa, from about 60 MPa to about 300 MPa, fromabout 70 MPa to about 300 MPa, from about 75 MPa to about 300 MPa, fromabout 80 MPa to about 300 MPa, from about 90 MPa to about 300 MPa, fromabout 100 MPa to about 300 MPa, from about 1100 MPa to about 300 MPa,from about 120 MPa to about 300 MPa, from about 130 MPa to about 300MPa, or from about 150 MPa to about 300 MPa.

In one or more embodiments, the stress profile 312 may be described asparabolic-like in shape. In some embodiments, the stress profile alongthe region or depth of the glass-based article exhibiting tensile stressexhibits a parabolic-like shape. In one or more specific embodiments,the stress profile 312 is free of a flat stress (either compressive ortensile) portion or a portion that exhibits a substantially constantstress (either compressive or tensile). In some embodiments, the CTregion exhibits a stress profile that is substantially free of a flatstress or free of a substantially constant stress. In one or moreembodiments, all points of the stress profile 312 between a thicknessrange from about 0t up to about 0.2·t and greater than 0.8·t to t (orfrom about 0·t to about 0.3·t and greater than 0.7.0 comprise a tangenthaving a slope that is less than about −0.1 MPa/micrometer or greaterthan about 0.1 MPa/micrometer. In some embodiments, the slope of thetangent may be less than about −0.2 MPa/micrometer or greater than about0.2 MPa/micrometer. In some more specific embodiments, the slope of thetangent may be less than about −0.3 MPa/micrometer or greater than about0.3 MPa/micrometer. In even more specific embodiments, the slope of thetangent may be less than about −0.5 MPa/micrometer or greater than about0.5 MPa/micrometer. In other words, the stress profile of one or moreembodiments along these thickness ranges (i.e., 0·t up to about 0.2·tand greater than 0.8t, or from about 0t to about 0.3·t and 0.7·t orgreater) exclude points having a tangent with zero slope, or slopeapproximating zero, or flat slope. Without being bound by theory, knownerror function or quasi-linear stress profiles have points along thesethickness ranges (i.e., from about 0·t up to about 0.2·t and greaterthan 0.8·t, or from about 0·t to about 0.3·t and 0.7·t or greater) thathave a tangent with a slope zero or of a value that is close to zero,i.e., that is in the range from greater than about −0.1 MPa/micrometerto less than about 0.1 MPa/micrometer (indicating a flat or zero slopestress profile along such thickness ranges, as shown in FIG. 2, 220).The glass-based articles of one or more embodiments of this disclosuredo not exhibit such a stress profile having a flat or zero slope stressprofile along these thickness ranges, as shown in FIG. 3.

In one or more embodiments, the glass-based article exhibits a stressprofile in a thickness range from about 0.1·t to 0.3·t and from about0.7·t to 0.9·t that comprises a maximum-slope tangent and aminimum-slope tangent. In some instances, the difference between themaximum-slope tangent and the minimum-slope tangent is about 3.5MPa/micrometer or less, about 3 MPa/micrometer or less, about 2.5MPa/micrometer or less, or about 2 MPa/micrometer or less.

In one or more embodiments, the glass-based article includes a stressprofile 312 that is substantially free of any flat segments that extendin a depth direction or along at least a portion of the thickness t ofthe glass-based article. In other words, the stress profile 312 issubstantially continuously increasing or decreasing along the thicknesst. In some embodiments, the stress profile is substantially free of anyflat segments in a depth direction having a length of about 10micrometers or more, about 50 micrometers or more, or about 100micrometers or more, or about 200 micrometers or more. As used herein,the term “flat” refers to a slope having a magnitude of less than about0.5 MPa/micrometer, or less than about 0.2 MPa/micrometer along the flatsegment. In some embodiments, one or more portions of the stress profilethat are substantially free of any flat segments in a depth directionare present at depths within the glass-based article of about 5micrometers or greater (e.g., 10 micrometers or greater, or 15micrometers or greater) from either one or both the first surface or thesecond surface. For example, along a depth of about 0 micrometers toless than about 5 micrometers from the first surface, the stress profilemay include linear segments, but from a depth of about 5 micrometers orgreater from the first surface, the stress profile may be substantiallyfree of flat segments. As used herein “linear” includes line segmentshaving flat slope as well as line segments not having flat slopes; forexample of the latter, see FIG. 11 within a depth of about 12 micronsfrom the surface.

In some embodiments, the stress profile may include linear segments atdepths from about 0t up to about 0.1t and may be substantially free offlat segments at depths of about 0.1t to about 0.4t. In someembodiments, the stress profile for a thickness in the range from about0t to about 0.1t may have a slope whose magnitude (in absolute value) isin the range from about 20 MPa/micron to about 200 MPa/micron. As willbe described herein, such embodiments may be formed using a singleion-exchange process by which the bath includes two or more alkali saltsor is a mixed alkali salt bath or multiple (e.g., 2 or more) ionexchange processes.

In one or more embodiments, the glass-based article may be described interms of the shape of the stress profile along the CT region (327 inFIG. 3). For example, in some embodiments, the stress profile along theCT region (where stress is in tension) may be approximated by Equation(1):

Stress(x)=MaxT−(((CT_(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(n))  (1)

In Equation (1), the stress (x) is the stress value at position x. Herethe stress is positive (tension). In Equation (1), MaxT is the maximumtension value and CT_(n) is the tension value at n and is less than orequal to MaxT. Both MaxT and CT_(n) are positive values in MPa. Thevalue x is position along the thickness (t) in micrometers, with a rangefrom 0 to t; x=0 is one surface (302, in FIG. 3), x=0.5t is the centerof the glass-based article (at which position stress(x)=MaxT), and x=tis the opposite surface (304, in FIG. 3). MaxT used in Equation (1) isequivalent to the maximum CT, which may be less than about 71.5/√(t). Insome embodiments, the MaxT used in Equation (1) may be in the range fromabout 50 MPa to about 80 MPa (e.g., from about 60 MPa to about 80 MPa,from about 70 MPa to about 80 MPa, from about 50 MPa to about 75 MPa,from about 50 MPa to about 70 MPa, or from about 50 MPa to about 65MPa), and n is a fitting parameter from 1.5 to 5 (e.g., 2 to 4, 2 to 3or 1.8 to 2.2) or from about 1.5 to about 2. In one or more embodiments,n=2 can provide a parabolic stress profile, exponents that deviate fromn=2 provide stress profiles with near parabolic stress profiles. FIG. 4is a graph illustrating various stress profiles according to one or moreembodiments of this disclosure, based on changes in the fittingparameter n.

In one or more embodiments, CTn may be less than MaxT where there is acompressive stress spike on one or both major surfaces of theglass-based article. In one or more embodiments, CTn is equal to MaxTwhen there is no compressive stress spike on one or both major surfacesof the glass-based article.

In some embodiments, the stress profile may be modified by heattreatment. In such embodiments, the heat treatment may occur before anyion-exchange processes, between ion-exchange processes, or after allion-exchange processes. In some embodiments, the heat treatment mayreduce the absolute value of the magnitude of the slope of the stressprofile at or near the surface. In some embodiments, where a steeper orgreater slope is desired at the surface, an ion-exchange process afterthe heat treatment may be utilized to provide a “spike” or to increasethe slope of the stress profile at or near the surface.

In one or more embodiments, the stress profile 312 is generated due to anon-zero concentration of a metal oxide(s) that varies along a portionof the thickness. As mentioned above, the variation in metal oxideconcentration may be referred to herein as a metal oxide concentrationgradient. In some embodiments, the concentration of a metal oxide isnon-zero and varies, both along a thickness range from about 0·t toabout 0.3·t. In some embodiments, the concentration of the metal oxideis non-zero and varies along a thickness range from about 0·t to about0.35·t, from about 0·t to about 0.4·t, from about 0·t to about 0.45·t orfrom about 0·t to about 0.48·t. The metal oxide may be described asgenerating a stress in the glass-based article. The variation inconcentration may be continuous along the above-referenced thicknessranges. Variation in concentration may include a change in metal oxideconcentration of about 0.2 mol % along a thickness segment of about 100micrometers. This change may be measured by known methods in the artincluding microprobe, as shown in Example 1. The metal oxide that isnon-zero in concentration and varies along a portion of the thicknessmay be described as generating a stress in the glass-based article.

The variation in concentration may be continuous along theabove-referenced thickness ranges. In some embodiments, the variation inconcentration may be continuous along thickness segments in the rangefrom about 10 micrometers to about 30 micrometers. In some embodiments,the concentration of the metal oxide decreases from the first surface toa point between the first surface and the second surface and increasesfrom the point to the second surface.

The concentration of metal oxide may include more than one metal oxide(e.g., a combination of Na₂O and K₂O). In some embodiments, where twometal oxides are utilized and where the radius of the ions differ fromone or another, the concentration of ions having a larger radius isgreater than the concentration of ions having a smaller radius atshallow depths, while the at deeper depths, the concentration of ionshaving a smaller radius is greater than the concentration of ions havinglarger radius. For example, where a single Na- and K-containing bath isused in the ion exchange process, the concentration of K+ ions in theglass-based article is greater than the concentration of Na+ ions atshallower depths, while the concentration of Na+ is greater than theconcentration of K+ ions at deeper depths. This is due, in part, due tothe size of the monovalent ions that are exchanged into the glass forsmaller monovalent ions. In such glass-based articles, the area at ornear the surface comprises a greater CS due to the greater amount oflarger ions (i.e., K+ ions) at or near the surface. This greater CS maybe exhibited by a stress profile having a steeper slope at or near thesurface (i.e., a spike in the stress profile at the surface).

The concentration gradient or variation of one or more metal oxides iscreated by chemically strengthening a glass-based substrate, aspreviously described herein, in which a plurality of first metal ions inthe glass-based substrate is exchanged with a plurality of second metalions. The first ions may be ions of lithium, sodium, potassium, andrubidium. The second metal ions may be ions of one of sodium, potassium,rubidium, and cesium, with the proviso that the second alkali metal ionhas an ionic radius greater than the ionic radius of the first alkalimetal ion. The second metal ion is present in the glass-based substrateas an oxide thereof (e.g., Na₂O, K₂O, Rb₂O, Cs₂O or a combinationthereof).

In one or more embodiments, the metal oxide concentration gradientextends through a substantial portion of the thickness t or the entirethickness t of the glass-based article, including the CT layer 327. Inone or more embodiments, the concentration of the metal oxide is about0.5 mol % or greater in the CT layer 327. In some embodiments, theconcentration of the metal oxide may be about 0.5 mol % or greater(e.g., about 1 mol % or greater) along the entire thickness of theglass-based article, and is greatest at the first surface 302 and/or thesecond surface 304 and decreases substantially constantly to a pointbetween the first surface 302 and the second surface 304. At that point,the concentration of the metal oxide is the least along the entirethickness t; however the concentration is also non-zero at that point.In other words, the non-zero concentration of that particular metaloxide extends along a substantial portion of the thickness t (asdescribed herein) or the entire thickness t. In some embodiments, thelowest concentration in the particular metal oxide is in the CT layer327. The total concentration of the particular metal oxide in theglass-based article may be in the range from about 1 mol % to about 20mol %.

In one or more embodiments, the glass-based article includes a firstmetal oxide concentration and a second metal oxide concentration, suchthat the first metal oxide concentration is in the range from about 0mol % to about 15 mol % along a first thickness range from about 0t toabout 0.5t, and the second metal oxide concentration is in the rangefrom about 0 mol % to about 10 mol % from a second thickness range fromabout 0 micrometers to about 25 micrometers (or from about 0 micrometersto about 12 micrometers); however, the concentration of one or both thefirst metal oxide and the second metal oxide is non-zero along asubstantial portion or the entire thickness of the glass-based article.The glass-based article may include an optional third metal oxideconcentration. The first metal oxide may include Na₂O while the secondmetal oxide may include K₂O.

The concentration of the metal oxide may be determined from a baselineamount of the metal oxide in the glass-based article prior to beingmodified to include the concentration gradient of such metal oxide.

In one or more embodiments, the glass-based articles may be described interms of how they fracture and the fragments that result from suchfracture, as measured by the “Frangibility Test”, as described Z. Tang,et al. Automated Apparatus for Measuring the Frangibility andFragmentation of Strengthened Glass. Experimental Mechanics (2014)54:903-912. In one or more embodiments, when fractured, the glass-basedarticles fracture into 2 or less fragments per square inch (or per6.4516 square centimeters) of the glass-based article (prior tofracture), wherein the sample size used was a 5 cm by 5 cm (2 inch by 2inch) square.

In one or more embodiments, after chemically strengthening theglass-based article, the resulting stress profile 312 of the glass-basedarticle provides improved fracture resistance. For example, in someembodiments, upon fracture, the glass-based article comprises fragmentshaving an average longest cross-sectional dimension of less than orequal to about 2·t (e.g., 1.8·t, 1.6·t, 1.5·t, 1.4·t, 1.2·t or 1·t orless) as measured by the “Frangibility Test”, as described Z. Tang, etal. Automated Apparatus for Measuring the Frangibility and Fragmentationof Strengthened Glass. Experimental Mechanics (2014) 54:903-912. Thenumber of fragments is divided by the area of the sample being tested(in square inches), wherein the sample size used was a 5 cm by 5 cm (2inch by 2 inch) square.

In one or more embodiments, the glass-based articles may exhibit afracture toughness (K_(1C)) of about 0.7 MPa·m^(1/2) or greater. In somecases, the fracture toughness may be about 0.8 MPa·m^(1/2) or greater,or about 0.9 MPa·m^(1/2) or greater. In some embodiments the fracturetoughness may be in the range from about 0.7 MPa·m^(1/2) to about 1MPa·m^(1/2).

In some embodiments, the substrate may also be characterized as having ahardness from about 500 HVN to about 800 HVN (kgf/mm²), as measured byVicker's hardness test at a load of 200 g. In some embodiments, theglass-based article may include a Vicker's hardness is in the range fromabout 600 HVN to about 800 HVN.

The glass-based articles described herein may exhibit a stored tensileenergy in the range from greater than 0 J/m² to about 40 J/m². In someinstances, the stored tensile energy may be in the range from about 5J/m² to about 40 J/m², from about 10 J/m² to about 40 J/m², from about15 J/m² to about 40 J/m², from about 20 J/m² to about 40 J/m², fromabout 1 J/m² to about 35 J/m², from about 1 J/m² to about 30 J/m², fromabout 1 J/m² to about 25 J/m², from about 1 J/m² to about 20 J/m², fromabout 1 J/m² to about 15 J/m², from about 1 J/m² to about 10 J/m², fromabout 10 J/m² to about 30 J/m², from about 10 J/m² to about 25 J/m²,from about 15 J/m² to about 30 J/m², from about 15 J/m² to about 25J/m², from about 18 J/m² to about 22 J/m², from about 25 J/m² to about40 J/m², or from about 25 J/m² to about 30 J/m². The thermally andchemically strengthened glass-based articles of one or more embodimentsmay exhibit a stored tensile energy of about 6 J/m² or greater, about 10J/m² or greater, about 15 J/m² or greater, or about 20 J/m² or greater.

Stored tensile energy is calculated using the following Equation (2):

stored tensile energy (J/m²)=[(1−ν)/E]∫(σ̂2)(dt)  (2)

where ν is Poisson's ratio, E is the Young's modulus (in MPa), σ isstress (in MPa) and the integration is computed across the thickness (inmicrons) of the tensile region only.

The glass-based articles described herein generally have Young's modulusor Young's modulus of less than about 80 GPa (e.g., about 75 GPa orless, about 70 GPa or less, about 65 GPa or less, or about 60 GPa orless). The lower limit of the Young's modulus may be greater than about65 GPa. The Young's modulus, which is intrinsic to the composition ofthe glass-based article, can provide the desired high stiffness, whichis an extrinsic property, to the ultimate glass-based article that isproduced therefrom.

In some embodiments, the glass-based article comprises a high liquidusviscosity that enables the formation of the glass-based articles viadown-draw techniques (e.g., fusion draw, slot draw, and other likemethods), which can provide high precision surface smoothness. As usedherein, the term “liquidus viscosity” refers to the viscosity of amolten glass at the liquidus temperature, wherein the term “liquidustemperature” refers to the temperature at which crystals first appear asa molten glass cools down from the melting temperature (or thetemperature at which the very last crystals melt away as temperature isincreased from room temperature). The liquidus viscosity is determinedby the following method. First the liquidus temperature of the glass ismeasured in accordance with ASTM C829-81 (2015), titled “StandardPractice for Measurement of Liquidus Temperature of Glass by theGradient Furnace Method”. Next the viscosity of the glass at theliquidus temperature is measured in accordance with ASTM C965-96(2012),titled “Standard Practice for Measuring Viscosity of Glass Above theSoftening Point”. In general, the glass-based articles (or thecompositions used to form such articles) described herein a liquidusviscosity of about 100 kilopoise (kP) or greater. In scenarios where ahigher liquidus viscosity is desired for down-draw processability, theglass-based articles (or the compositions used to form such articles)exhibit a liquidus viscosity of about 200 kP or more (e.g., about 600 kPor greater).

In one or more embodiments, the glass-based articles exhibit a KnoopLateral Cracking Scratch Threshold in the range from about 4 N to about7 N, from about 4.5 N to about 7 N, from about 5 N to about 7 N, fromabout 4 N to about 6.5 N, from about 4 N to about 6 N, or from about 5 Nto about 6 N. As used herein, Knoop Scratch Lateral Cracking Thresholdis the onset of lateral cracking (in 3 or more of 5 indentation events).In Knoop Lateral Cracking Scratch Threshold testing, samples of theglass substrates and articles were first scratched with a Knoop indenterunder a dynamic or ramped load to identify the lateral crack onset loadrange for the sample population. Once the applicable load range isidentified, a series of increasing constant load scratches (3 minimum ormore per load) are performed to identify the Knoop scratch threshold.The Knoop scratch threshold range can be determined by comparing thetest specimen to one of the following 3 failure modes: 1) sustainedlateral surface cracks that are more than two times the width of thegroove, 2) damage is contained within the groove, but there are lateralsurface cracks that are less than two times the width of groove andthere is damage visible by naked eye, or 3) the presence of largesubsurface lateral cracks which are greater than two times the width ofgroove and/or there is a median crack at the vertex of the scratch.

In one or more embodiments, the glass-based articles exhibit a Vicker'sIndentation Fracture Threshold in the range from about 10 kgf orgreater, about 12 kgf or greater, or about 15 kgf or greater. As usedherein, Vicker's Indentation Fracture Threshold is the onset ofmedian/radial cracking (in 3 or more of 5 indentation events) extendingfrom at least one corner of the indentation site. In Vicker'sIndentation Fracture Threshold testing, samples of the glass substratesand articles were repeatedly indented with a diamond tip (at 136° angle)at increasing loads. Each indentation has the potential to produce 4radial cracks, one from each corner of the indent. By counting theaverage number of radial cracks at each indentation load, the crackingthreshold is the load at which there is an average of 2 cracks perindent (or the 50% cracking threshold).

In one or more embodiments, the scratch resistance of the glass-basedarticles described herein may be measured by sliding a 500-micrometerglass ball having the same composition as the glass-based substratesdescribed herein. For example, the composition of the ball may includeabout 64 mol % SiO₂, 15.67 mol % Al₂O₃, 6.4 mol % Li₂O, 10.8 mol % Na₂O,1.2 mol % ZnO, 0.04 mol % SnO₂, and 2.5 mol % P₂O₅. FIGS. 5A-B show themaximum tensile stress applied to the surface (in MPa) from the glassball as it is applied to the surface of a glass-based article of one ormore embodiments. In FIGS. 5A-5B, the contact stress (diamond datapoints) and sliding contact force assuming a coefficient of friction of0.1 (square data points) and coefficient of friction of 0.2 (triangledata points), are shown as a function of normal load (N) applied. InFIG. 5A, the glass-based article had a surface CS of about 500 MPa. InFIG. 5B, the glass-based article had a surface CS of about 750 MPa.

In one or more embodiments, the glass-based articles exhibit improvedsurface strength when subjected to abraded ring-on-ring (AROR) testing.The strength of a material is the stress at which fracture occurs. TheAROR test is a surface strength measurement for testing flat glassspecimens, and ASTM C1499-09(2013), entitled “Standard Test Method forMonotonic Equibiaxial Flexural Strength of Advanced Ceramics at AmbientTemperature,” serves as the basis for the AROR test methodologydescribed herein. The contents of ASTM C1499-09 are incorporated hereinby reference in their entirety. In one embodiment, the glass specimen isabraded prior to ring-on-ring testing with 90 grit silicon carbide (SiC)particles that are delivered to the glass sample using the method andapparatus described in Annex A2, entitled “abrasion Procedures,” of ASTMC158-02(2012), entitled “Standard Test Methods for Strength of Glass byFlexure (Determination of Modulus of Rupture). The contents of ASTMC158-02 and the contents of Annex 2 in particular are incorporatedherein by reference in their entirety.

Prior to ring-on-ring testing a surface of the glass-based article isabraded as described in ASTM C158-02, Annex 2, to normalize and/orcontrol the surface defect condition of the sample using the apparatusshown in Figure A2.1 of ASTM C158-02. The abrasive material is typicallysandblasted onto the surface 110 of the glass-based article at a load of15 psi using an air pressure of 304 kPa (44 psi); although in theExamples below, the abrasive material was sandblasted onto the surface110 at other loads (e.g., 25 psi or 45 psi). After air flow isestablished, 5 cm³ of abrasive material is dumped into a funnel and thesample is sandblasted for 5 seconds after introduction of the abrasivematerial.

For the AROR test, a glass-based article having at least one abradedsurface 410 as shown in FIG. 6 is placed between two concentric rings ofdiffering size to determine equibiaxial flexural strength (i.e., themaximum stress that a material is capable of sustaining when subjectedto flexure between two concentric rings), as also shown in FIG. 6. Inthe AROR configuration 400, the abraded glass-based article 410 issupported by a support ring 420 having a diameter D2. A force F isapplied by a load cell (not shown) to the surface of the glass-basedarticle by a loading ring 430 having a diameter D1.

The ratio of diameters of the loading ring and support ring D1/D2 may bein a range from about 0.2 to about 0.5. In some embodiments, D1/D2 isabout 0.5. Loading and support rings 130, 120 should be alignedconcentrically to within 0.5% of support ring diameter D2. The load cellused for testing should be accurate to within ±1% at any load within aselected range. In some embodiments, testing is carried out at atemperature of 23±2° C. and a relative humidity of 40±10%.

For fixture design, the radius r of the protruding surface of theloading ring 430, h/2≦r≦3h/2, where his the thickness of glass-basedarticle 410. Loading and support rings 430, 420 are typically made ofhardened steel with hardness HRc>40. AROR fixtures are commerciallyavailable.

The intended failure mechanism for the AROR test is to observe fractureof the glass-based article 410 originating from the surface 430 a withinthe loading ring 430. Failures that occur outside of this region—i.e.,between the loading rings 430 and support rings 420—are omitted fromdata analysis. Due to the thinness and high strength of the glass-basedarticle 410, however, large deflections that exceed ½ of the specimenthickness h are sometimes observed. It is therefore not uncommon toobserve a high percentage of failures originating from underneath theloading ring 430. Stress cannot be accurately calculated withoutknowledge of stress development both inside and under the ring(collected via strain gauge analysis) and the origin of failure in eachspecimen. AROR testing therefore focuses on peak load at failure as themeasured response.

The strength of glass-based article depends on the presence of surfaceflaws. However, the likelihood of a flaw of a given size being presentcannot be precisely predicted, as the strength of glass is statisticalin nature. A probability distribution can therefore generally be used asa statistical representation of the data obtained.

In some embodiments, the glass-based articles described herein have asurface or equibiaxial flexural strength of 20 kgf or more, and up toabout 30 kgf as determined by AROR testing using a load of 25 psi oreven 45 psi to abrade the surface. In other embodiments, the surfacestrength is 25 kgf or more, and in still other embodiments, 30 kgf ormore.

In some embodiments, the glass-based articles described herein may bedescribed in terms of performance in an inverted ball on sandpaper(IBoS) test. The IBoS test is a dynamic component level test that mimicsthe dominant mechanism for failure due to damage introduction plusbending that typically occurs in glass-based articles that are used inmobile or hand held electronic devices, as schematically shown in FIG.7. In the field, damage introduction (a in FIG. 8) occurs on the topsurface of the glass-based article. Fracture initiates on the topsurface of the glass-based article and damage either penetrates theglass-based article (b in FIG. 8) or the fracture propagates frombending on the top surface or from the interior portions of theglass-based article (c in FIG. 8). The IBoS test is designed tosimultaneously introduce damage to the surface of the glass and applybending under dynamic load. In some instances, the glass-based articleexhibits improved drop performance when it includes a compressive stressthan if the same glass-based article does not include a compressivestress.

An IBoS test apparatus is schematically shown in FIG. 6. Apparatus 500includes a test stand 510 and a ball 530. Ball 530 is a rigid or solidball such as, for example, a stainless steel ball, or the like. In oneembodiment, ball 530 is a 4.2 gram stainless steel ball having diameterof 10 mm. The ball 530 is dropped directly onto the glass-based articlesample 518 from a predetermined height h. Test stand 510 includes asolid base 512 comprising a hard, rigid material such as granite or thelike. A sheet 514 having an abrasive material disposed on a surface isplaced on the upper surface of the solid base 512 such that surface withthe abrasive material faces upward. In some embodiments, sheet 514 issandpaper having a 30 grit surface and, in other embodiments, a 180 gritsurface. The glass-based article sample 518 is held in place above sheet514 by sample holder 515 such that an air gap 516 exists betweenglass-based article sample 518 and sheet 514. The air gap 516 betweensheet 514 and glass-based article sample 518 allows the glass-basedarticle sample 518 to bend upon impact by ball 530 and onto the abrasivesurface of sheet 514. In one embodiment, the glass-based article sample218 is clamped across all corners to keep bending contained only to thepoint of ball impact and to ensure repeatability. In some embodiments,sample holder 514 and test stand 510 are adapted to accommodate samplethicknesses of up to about 2 mm. The air gap 516 is in a range fromabout 50 μm to about 100 μm. Air gap 516 is adapted to adjust fordifference of material stiffness (Young's modulus, Emod), but alsoincludes the Young's modulus and thickness of the sample. An adhesivetape 520 may be used to cover the upper surface of the glass-basedarticle sample to collect fragments in the event of fracture of theglass-based article sample 518 upon impact of ball 530.

Various materials may be used as the abrasive surface. In a oneparticular embodiment, the abrasive surface is sandpaper, such assilicon carbide or alumina sandpaper, engineered sandpaper, or anyabrasive material known to those skilled in the art for havingcomparable hardness and/or sharpness. In some embodiments, sandpaperhaving 30 grit may be used, as it has a surface topography that is moreconsistent than either concrete or asphalt, and a particle size andsharpness that produces the desired level of specimen surface damage.

In one aspect, a method 600 of conducting the IBoS test using theapparatus 500 described hereinabove is shown in FIG. 9. In Step 610, aglass-based article sample (218 in FIG. 6) is placed in the test stand510, described previously and secured in sample holder 515 such that anair gap 516 is formed between the glass-based article sample 518 andsheet 514 with an abrasive surface. Method 600 presumes that the sheet514 with an abrasive surface has already been placed in test stand 510.In some embodiments, however, the method may include placing sheet 514in test stand 510 such that the surface with abrasive material facesupward. In some embodiments (Step 610 a), an adhesive tape 520 isapplied to the upper surface of the glass-based article sample 518 priorto securing the glass-based article sample 518 in the sample holder 510.

In Step 520, a solid ball 530 of predetermined mass and size is droppedfrom a predetermined height h onto the upper surface of the glass-basedarticle sample 518, such that the ball 530 impacts the upper surface (oradhesive tape 520 affixed to the upper surface) at approximately thecenter (i.e., within 1 mm, or within 3 mm, or within 5 mm, or within 10mm of the center) of the upper surface. Following impact in Step 520,the extent of damage to the glass-based article sample 518 is determined(Step 630). As previously described hereinabove, herein, the term“fracture” means that a crack propagates across the entire thicknessand/or entire surface of a substrate when the substrate is dropped orimpacted by an object.

In method 600, the sheet 518 with the abrasive surface may be replacedafter each drop to avoid “aging” effects that have been observed inrepeated use of other types (e.g., concrete or asphalt) of drop testsurfaces.

Various predetermined drop heights h and increments are typically usedin method 600. The test may, for example, utilize a minimum drop heightto start (e.g., about 10-20 cm). The height may then be increased forsuccessive drops by either a set increment or variable increments. Thetest described in method 600 is stopped once the glass-based articlesample 518 breaks or fractures (Step 631). Alternatively, if the dropheight h reaches the maximum drop height (e.g., about 100 cm) withoutfracture, the drop test of method 300 may also be stopped, or Step 520may be repeated at the maximum height until fracture occurs.

In some embodiments, IBoS test of method 600 is performed only once oneach glass-based article sample 518 at each predetermined height h. Inother embodiments, however, each sample may be subjected to multipletests at each height.

If fracture of the glass-based article sample 518 has occurred (Step 631in FIG. 9), the IBoS test according to method 600 is ended (Step 640).If no fracture resulting from the ball drop at the predetermined dropheight is observed (Step 632), the drop height is increased by apredetermined increment (Step 634)—such as, for example 5, 10, or 20cm—and Steps 620 and 630 are repeated until either sample fracture isobserved (631) or the maximum test height is reached (636) withoutsample fracture. When either Step 631 or 636 is reached, the testaccording to method 600 is ended.

When subjected to the inverted ball on sandpaper (IBoS) test describedabove, embodiments of the glass-based article described herein haveabout a 60% or more survival rate when the ball is dropped onto thesurface of the glass from a height of 100 cm. For example, a glass-basedarticle is described as having a 60% survival rate when dropped from agiven height when three of five identical (or nearly identical) samples(i.e., having approximately the same composition and, when strengthened,approximately the same compressive stress and depth of compression orcompressive stress layer, as described herein) survive the IBoS droptest without fracture when dropped from the prescribed height (here 100cm). In other embodiments, the survival rate in the 100 cm IBoS test ofthe glass-based articles that are strengthened is about 70% or more, inother embodiments, about 80% or more, and, in still other embodiments,about 90% or more. In other embodiments, the survival rate of thestrengthened glass-based articles dropped from a height of 100 cm in theIBoS test is about 60% or more, in other embodiments, about 70% or more,in still other embodiments, about 80% or more, and, in otherembodiments, about 90% or more. In one or more embodiments, the survivalrate of the strengthened glass-based articles dropped from a height of150 cm in the IBoS test is about 60% or more, in other embodiments,about 70% or more, in still other embodiments, about 80% or more, and,in other embodiments, about 90% or more.

To determine the survivability rate of the glass-based articles whendropped from a predetermined height using the IBoS test method andapparatus described hereinabove, at least five identical (or nearlyidentical) samples (i.e., having approximately the same composition and,if strengthened, approximately the same compressive stress and depth ofcompression or layer) of the glass-based articles are tested, althoughlarger numbers (e.g., 10, 20, 30, etc.) of samples may be subjected totesting to raise the confidence level of the test results. Each sampleis dropped a single time from the predetermined height (e.g., 100 cm or150 cm) or, alternatively, dropped from progressively higher heightswithout fracture until the predetermined height is reached, and visually(i.e., with the naked eye) examined for evidence of fracture (crackformation and propagation across the entire thickness and/or entiresurface of a sample). A sample is deemed to have “survived” the droptest if no fracture is observed after being dropped from thepredetermined height, and a sample is deemed to have “failed (or “notsurvived”) if fracture is observed when the sample is dropped from aheight that is less than or equal to the predetermined height. Thesurvivability rate is determined to be the percentage of the samplepopulation that survived the drop test. For example, if 7 samples out ofa group of 10 did not fracture when dropped from the predeterminedheight, the survivability rate of the glass would be 70%.

The glass-based articles described herein may be transparent. In one ormore the glass-based article may have a thickness of about 1 millimeteror less and exhibit a transmittance of about 88% or greater over awavelength in the range from about 380 nm to about 780 nm.

The glass-based article may also exhibit a substantially white color.For example, the glass-based article may exhibit CIELAB color spacecoordinates, under a CIE illuminant F02, of L* values of about 88 andgreater, a* values in the range from about −3 to about +3, and b* valuesin the range from about −6 to about +6.

Choice of substrates not particularly limited. In some examples, theglass-based article may be described as having a high cation diffusivityfor ion exchange. In one or more embodiments, the glass or glass-ceramichas fast ion-exchange capability, i.e., where diffusivity is greaterthan 500 μm²/hr or may be characterized as greater than 450 μm²/hour at460° C. In one or more embodiments, the glass or glass-ceramic exhibitsa sodium ion diffusivity that is about 450 μm²/hour or greater at 460°C. or is about 500 μm²/hour or greater at 460° C. In one or moreembodiments, the glass or glass-ceramic exhibits a potassium iondiffusivity that is about 450 μm²/hour or greater at 460° C. or is about500 μm²/hour or greater at 460° C.

The glass-based article may include an amorphous substrate, acrystalline substrate or a combination thereof (e.g., a glass-ceramicsubstrate). In one or more embodiments, the glass-based articlesubstrate (prior to being chemically strengthened as described herein)may include a glass composition, in mole percent (mole %), including:SiO₂ in the range from about 40 to about 80, Al₂O₃ in the range fromabout 10 to about 30, B₂O₃ in the range from about 0 to about 10, R₂O inthe range from about 0 to about 20, and RO in the range from about 0 toabout 15. As used herein, R₂O refers to the total amount of alkali metaloxides such as Li₂O, Na₂O, K₂O, Rb₂O, and Cs₂O. As used herein RO refersto the total amount of alkaline earth metal oxides such as MgO, CaO,SrO, BaO, ZnO and the like. In some instances, the composition mayinclude either one or both of ZrO₂ in the range from about 0 mol % toabout 5 mol % and P₂O₅ in the range from about 0 to about 15 mol %. TiO₂can be present from about 0 mol % to about 2 mol %.

In some embodiments, the glass composition may include SiO₂ in anamount, in mol %, in the range from about 45 to about 80, from about 45to about 75, from about 45 to about 70, from about 45 to about 65, fromabout 45 to about 60, from about 45 to about 65, from about 45 to about65, from about 50 to about 70, from about 55 to about 70, from about 60to about 70, from about 70 to about 75, from about 70 to about 72, fromabout 50 to about 65, or from about 60 to about 65.

In some embodiments, the glass composition may include Al₂O₃ in anamount, in mol %, in the range from about 5 to about 28, from about 5 toabout 26, from about 5 to about 25, from about 5 to about 24, from about5 to about 22, from about 5 to about 20, from about 6 to about 30, fromabout 8 to about 30, from about 10 to about 30, from about 12 to about30, from about 14 to about 30, 15 to about 30, or from about 12 to about18.

In one or more embodiments, the glass composition may include B₂O₃ in anamount, in mol %, in the range from about 0 to about 8, from about 0 toabout 6, from about 0 to about 4, from about 0.1 to about 8, from about0.1 to about 6, from about 0.1 to about 4, from about 1 to about 10,from about 2 to about 10, from about 4 to about 10, from about 2 toabout 8, from about 0.1 to about 5, or from about 1 to about 3. In someinstances, the glass composition may be substantially free of B₂O₃. Asused herein, the phrase “substantially free” with respect to thecomponents of the composition means that the component is not activelyor intentionally added to the composition during initial batching, butmay be present as an impurity in an amount less than about 0.001 mol %.

In some embodiments, the glass composition may include one or morealkali earth metal oxides, such as MgO, CaO and ZnO. In someembodiments, the total amount of the one or more alkali earth metaloxides may be a non-zero amount up to about 15 mol %. In one or morespecific embodiments, the total amount of any of the alkali earth metaloxides may be a non-zero amount up to about 14 mol %, up to about 12 mol%, up to about 10 mol %, up to about 8 mol %, up to about 6 mol %, up toabout 4 mol %, up to about 2 mol %, or up about 1.5 mol %. In someembodiments, the total amount, in mol %, of the one or more alkali earthmetal oxides may be in the range from about 0.01 to 10, from about 0.01to 8, from about 0.01 to 6, from about 0.01 to 5, from about 0.05 to 10,from about 0.05 to 2, or from about 0.05 to 1. The amount of MgO may bein the range from about 0 mol % to about 5 mol % (e.g., from about 0.001to about 1, from about 0.01 to about 2, or from about 2 mol % to about 4mol %). The amount of ZnO may be in the range from about 0 to about 2mol % (e.g., from about 1 mol % to about 2 mol %). The amount of CaO maybe from about 0 mol % to about 2 mol %. In one or more embodiments, theglass composition may include MgO and may be substantially free of CaOand ZnO. In one variant, the glass composition may include any one ofCaO or ZnO and may be substantially free of the others of MgO, CaO andZnO. In one or more specific embodiments, the glass composition mayinclude only two of the alkali earth metal oxides of MgO, CaO and ZnOand may be substantially free of the third of the earth metal oxides.

The total amount, in mol %, of alkali metal oxides R₂O in the glasscomposition may be in the range from about 5 to about 20, from about 5to about 18, from about 5 to about 16, from about 5 to about 15, fromabout 5 to about 14, from about 5 to about 12, from about 5 to about 10,from about 5 to about 8, from about 5 to about 20, from about 6 to about20, from about 7 to about 20, from about 8 to about 20, from about 9 toabout 20, from about 10 to about 20, from about 11 to about 20, fromabout 12 to about 18, or from about 14 to about 18.

In one or more embodiments, the glass composition includes Na₂O in anamount in the range from about 0 mol % to about 18 mol %, from about 0mol % to about 16 mol % or from about 0 mol % to about 14 mol %, fromabout 0 mol % to about 12 mol %, from about 2 mol % to about 18 mol %,from about 4 mol % to about 18 mol %, from about 6 mol % to about 18 mol%, from about 8 mol % to about 18 mol %, from about 8 mol % to about 14mol %, from about 8 mol % to about 12 mol %, or from about 10 mol % toabout 12 mol %. In some embodiments, the composition may include about 4mol % or more Na₂O.

In some embodiments, the amount of Li₂O and Na₂O is controlled to aspecific amount or ratio to balance formability and ion exchangeability.For example, as the amount of Li₂O increases, the liquidus viscosity maybe reduced, thus preventing some forming methods from being used;however, such glass compositions are ion exchanged to deeper DOC levels,as described herein. The amount of Na₂O can modify liquidus viscositybut can inhibit ion exchange to deeper DOC levels.

In one or more embodiments, the glass composition may include K₂O in anamount less than about 5 mol %, less than about 4 mol %, less than about3 mol %, less than about 2 mol %, or less than about 1 mol %. In one ormore alternative embodiments, the glass composition may be substantiallyfree, as defined herein, of K₂O.

In one or more embodiments, the glass composition may include Li₂O in anamount about 0 mol % to about 18 mol %, from about 0 mol % to about 15mol % or from about 0 mol % to about 10 mol %, from about 0 mol % toabout 8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol %to about 4 mol % or from about 0 mol % to about 2 mol %. In someembodiments, the glass composition may include Li₂O in an amount about 2mol % to about 10 mol %, from about 4 mol % to about 10 mol %, fromabout 6 mol % to about 10 mol, or from about 5 mol % to about 8 mol %.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of Li₂O.

In one or more embodiments, the glass composition may include Fe₂O₃. Insuch embodiments, Fe₂O₃ may be present in an amount less than about 1mol %, less than about 0.9 mol %, less than about 0.8 mol %, less thanabout 0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %,less than about 0.4 mol %, less than about 0.3 mol %, less than about0.2 mol %, less than about 0.1 mol % and all ranges and sub-rangestherebetween. In one or more alternative embodiments, the glasscomposition may be substantially free, as defined herein, of Fe₂O₃.

In one or more embodiments, the glass composition may include ZrO₂. Insuch embodiments, ZrO₂ may be present in an amount less than about 1 mol%, less than about 0.9 mol %, less than about 0.8 mol %, less than about0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %, lessthan about 0.4 mol %, less than about 0.3 mol %, less than about 0.2 mol%, less than about 0.1 mol % and all ranges and sub-ranges therebetween.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of ZrO₂.

In one or more embodiments, the glass composition may include P₂O₅ in arange from about 0 mol % to about 10 mol %, from about 0 mol % to about8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol % toabout 4 mol %, from about 0.1 mol % to about 10 mol %, from about 0.1mol % to about 8 mol %, from about 2 mol % to about 8 mol %, from about2 mol % to about 6 mol % or from about 2 mol % to about 4 mol %. In someinstances, the glass composition may be substantially free of P₂O₅.

In one or more embodiments, the glass composition may include TiO₂. Insuch embodiments, TiO₂ may be present in an amount less than about 6 mol%, less than about 4 mol %, less than about 2 mol %, or less than about1 mol %. In one or more alternative embodiments, the glass compositionmay be substantially free, as defined herein, of TiO₂. In someembodiments, TiO₂ is present in an amount in the range from about 0.1mol % to about 6 mol %, or from about 0.1 mol % to about 4 mol %.

In some embodiments, the glass composition may include variouscompositional relationships. For example, the glass composition mayinclude a ratio of the amount of Li₂O (in mol %) to the total amount ofR₂O (in mol %) in the range from about 0 to about 1, from about 0 toabout 0.5, from about 0 to about 0.4, from about 0.1 to about 0.5, orfrom about 0.2 to about 0.4.

In some embodiments, the glass composition may include a differencebetween the total amount of R₂O (in mol %) to the amount of Al₂O₃ (inmol %) (R₂O−Al₂O₃) in the range from about 0 to about 5 (e.g., fromabout 0 to about 4, from about 0 to about 3, from about 0.1 to about 4,from about 0.1 to about 3, from about 0.1 to about 2 or from about 1 toabout 2).

In some embodiments, the glass composition may include a differencebetween the total amount of R_(x)O (in mol %) to the amount of Al₂O₃ (inmol %) (R_(x)O—Al₂O₃) in the range from about 0 to about 5 (e.g., fromabout 0 to about 4, from about 0 to about 3, from about 0.1 to about 4,from about 0.1 to about 3, from about 1 to about 3, or from about 2 toabout 3). As used herein, RxO includes R₂O and RO, as defined herein.

In some embodiments, the glass composition may include a ratio of thetotal amount of R₂O (in mol %) to the amount of Al₂O₃ (in mol %)(R₂O/Al₂O₃) in the range from about 0 to about 5 (e.g., from about 0 toabout 4, from about 0 to about 3, from about 1 to about 4, from about 1to about 3, or from about 1 to about 2).

In one or more embodiments, the glass composition includes a combinedamount of Al₂O₃ and Na₂O greater than about 15 mol % (e.g., greater than18 mol %, greater than about 20 mol %, or greater than about 23 mol %).The combined amount of Al₂O₃ and Na₂O may be up to and including about30 mol %, about 32 mol % or about 35 mol %.

The glass composition of one or more embodiments may exhibit a ratio ofthe amount of MgO (in mol %) to the total amount of RO (in mol %) in therange from about 0 to about 2.

In some embodiments, glass composition may be substantially free ofnucleating agents. Examples of typical nucleating agents are TiO₂, ZrO₂and the like. Nucleating agents may be described in terms of function inthat nucleating agents are constituents in the glass can initiate theformation of crystallites in the glass.

In some embodiments, the compositions used for the glass substrate maybe batched with from about 0 mol % to about 2 mol % of at least onefining agent selected from a group that includes Na₂SO₄, NaCl, NaF,NaBr, K₂SO₄, KCl, KF, KBr, and SnO₂. The glass composition according toone or more embodiments may further include SnO₂ in the range from about0 to about 2, from about 0 to about 1, from about 0.1 to about 2, fromabout 0.1 to about 1, or from about 1 to about 2. The glass compositionsdisclosed herein may be substantially free of As₂O₃ and/or Sb₂O₃.

In one or more embodiments, the composition may specifically includefrom about 62 mol % to 75 mol % SiO₂; from about 10.5 mol % to about 17mol % Al₂O₃; from about 5 mol % to about 13 mol % Li₂O; from about 0 mol% to about 4 mol % ZnO; from about 0 mol % to about 8 mol % MgO; fromabout 2 mol % to about 5 mol % TiO₂; from about 0 mol % to about 4 mol %B₂O₃; from about 0 mol % to about 5 mol % Na₂O; from about 0 mol % toabout 4 mol % K₂O; from about 0 mol % to about 2 mol % ZrO₂; from about0 mol % to about 7 mol % P₂O₅; from about 0 mol % to about 0.3 mol %Fe₂O₃; from about 0 mol % to about 2 mol % MnOx; and from about 0.05 mol% to about 0.2 mol % SnO₂.

In one or more embodiments, the composition may include from about 67mol % to about 74 mol % SiO₂; from about 11 mol % to about 15 mol %Al₂O₃; from about 5.5 mol % to about 9 mol % Li₂O; from about 0.5 mol %to about 2 mol % ZnO; from about 2 mol % to about 4.5 mol % MgO; fromabout 3 mol % to about 4.5 mol % TiO₂; from about 0 mol % to about 2.2mol % B₂O₃; from about 0 mol % to about 1 mol % Na₂O; from about 0 mol %to about 1 mol % K₂O; from about 0 mol % to about 1 mol % ZrO₂; fromabout 0 mol % to about 4 mol % P₂O₅; from about 0 mol % to about 0.1 mol% Fe₂O₃; from about 0 mol % to about 1.5 mol % MnOx; and from about 0.08mol % to about 0.16 mol % SnO₂.

In one or more embodiments, the composition may include from about 70mol % to 75 mol % SiO₂; from about 10 mol % to about 15 mol % Al₂O₃;from about 5 mol % to about 13 mol % Li₂O; from about 0 mol % to about 4mol % ZnO; from about 0.1 mol % to about 8 mol % MgO; from about 0 mol %to about 5 mol % TiO₂; from about 0.1 mol % to about 4 mol % B₂O₃; fromabout 0.1 mol % to about 5 mol % Na₂O; from about 0 mol % to about 4 mol% K₂O; from about 0 mol % to about 2 mol % ZrO₂; from about 0 mol % toabout 7 mol % P₂O₅; from about 0 mol % to about 0.3 mol % Fe₂O₃; fromabout 0 mol % to about 2 mol % MnOx; and from about 0.05 mol % to about0.2 mol % SnO₂.

In one or more embodiments, the composition may include from about 52mol % to about 65 mol % SiO₂; from about 14 mol % to about 18 mol %Al₂O₃; from about 5.5 mol % to about 7 mol % Li₂O; from about 1 mol % toabout 2 mol % ZnO; from about 0.01 mol % to about 2 mol % MgO; fromabout 4 mol % to about 12 mol % Na₂O; from about 0.1 mol % to about 4mol % P₂O₅; and from about 0.01 mol % to about 0.16 mol % SnO₂. In someembodiments, the composition may be substantially free of any one ormore of B₂O₃, TiO₂, K₂O and ZrO₂.

In one or more embodiments, the composition may include 0.5 mol % ormore P₂O₅, Na₂O and, optionally, Li₂O, where Li₂O (mol %)/Na₂O (mol%)<1. In addition, these compositions may be substantially free of B₂O₃and K₂O. In some embodiments, the composition may include ZnO, MgO, andSnO₂.

In some embodiments, the composition may comprise: from about 58 mol %to about 65 mol % SiO₂; from about 11 mol % to about 19 mol % Al₂O₃;from about 0.5 mol % to about 3 mol % P₂O₅; from about 6 mol % to about18 mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0 mol % toabout 6 mol % ZnO. In certain embodiments, the composition may comprisefrom about 63 mol % to about 65 mol % SiO₂; from 11 mol % to about 17mol % Al₂O₃; from about 1 mol % to about 3 mol % P₂O₅; from about 9 mol% to about 20 mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0mol % to about 6 mol % ZnO.

In some embodiments, the composition may include the followingcompositional relationships R₂O (mol %)/Al₂O₃ (mol %)<2, whereR₂O=Li₂O+Na₂O. In some embodiments, 65 mol %<SiO₂ (mol %)+P₂O₅ (mol%)<67 mol %. In certain embodiments, R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol%)+P₂O₅ (mol %)>−3 mol %, where R₂O=Li₂O+Na₂O and R′O is the totalamount of divalent metal oxides present in the composition.

Other exemplary compositions of glass-based articles prior to beingchemically strengthened, as described herein, are shown in Table 1A.Table 1B lists selected physical properties determined for the exampleslisted in Table 1A. The physical properties listed in Table 1B include:density; low temperature and high temperature CTE; strain, anneal andsoftening points; 10¹¹ Poise, 35 kP, 200 kP, liquidus, and zirconbreakdown temperatures; zircon breakdown and liquidus viscosities;Poisson's ratio; Young's modulus; refractive index, and stress opticalcoefficient. In some embodiments, the glass-based articles and glasssubstrates described herein have a high temperature CTE of less than orequal to 30 ppm/° C. and/or a Young's modulus of 70 GPa or more and, insome embodiments, a Young's modulus of up to 80 GPa.

TABLE 1A Exemplary compositions prior to chemical strengthening.Composition (mol %) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 SiO₂ 63.7764.03 63.67 63.91 64.16 63.21 63.50 Al₂O₃ 12.44 12.44 11.83 11.94 11.9411.57 11.73 P₂O₅ 2.43 2.29 2.36 2.38 1.92 1.93 1.93 Li₂O 0.00 0.00 0.000.00 0.00 0.00 0.00 Na₂O 16.80 16.81 16.88 16.78 16.80 17.63 16.85 ZnO0.00 4.37 0.00 4.93 0.00 5.59 5.93 MgO 4.52 0.02 5.21 0.02 5.13 0.020.01 SnO₂ 0.05 0.05 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.35 1.35 1.431.41 1.41 1.52 1.44 Li₂O/Na₂O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 (R₂O +RO) − Al₂O₃ − P₂O₅ 6.45 6.46 7.89 7.40 8.07 9.74 9.14 Composition (mol%) Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 SiO₂ 63.37 63.43 63.5663.58 63.66 63.62 63.67 Al₂O₃ 11.72 12.49 12.63 12.59 12.91 12.85 12.89P₂O₅ 2.00 2.32 2.46 2.46 2.43 2.45 2.47 Li₂O 0.00 0.00 1.42 2.87 0.001.42 2.92 Na₂O 16.84 17.16 15.45 14.04 16.89 15.48 13.92 ZnO 6.00 4.544.43 4.41 4.04 4.12 4.06 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02 SnO₂0.05 0.04 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.44 1.37 1.34 1.34 1.311.31 1.31 Li₂O/Na₂O 0.00 0.00 0.09 0.20 0.00 0.09 0.21 (R₂O + RO) −Al₂O₃ − P₂O₅ 9.14 6.90 6.22 6.29 5.62 5.72 5.57 Composition (mol %) Ex.15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 SiO₂ 63.55 63.80 63.7663.88 63.74 64.03 63.68 Al₂O₃ 12.92 12.90 12.95 13.48 13.37 13.26 13.19P₂O₅ 2.35 2.34 2.37 2.31 2.34 2.29 2.46 Li₂O 0.00 1.47 2.94 0.00 1.482.94 0.00 Na₂O 17.97 16.36 14.85 17.20 15.96 14.37 16.84 ZnO 0.00 0.000.00 0.00 0.00 0.00 3.77 MgO 3.17 3.08 3.09 3.08 3.08 3.06 0.02 SnO₂0.05 0.04 0.05 0.05 0.04 0.04 0.05 R₂O/Al₂O₃ 1.39 1.38 1.37 1.28 1.301.31 1.28 Li₂O/Na₂O 0.00 0.09 0.20 0.00 0.09 0.20 0.00 (R₂O + RO) −Al₂O₃ − P₂O₅ 5.87 5.67 5.56 4.48 4.81 4.83 4.98 Composition (mol %) Ex.22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 Ex. 27 Ex. 28 SiO₂ 63.66 63.76 63.6763.73 63.73 63.64 63.76 Al₂O₃ 14.15 15.31 13.87 14.82 12.93 16.62 16.59P₂O₅ 2.47 2.44 2.47 2.43 2.48 2.47 2.47 Li₂O 1.49 2.98 1.50 2.96 0.002.52 4.91 Na₂O 15.31 13.79 15.36 13.93 16.83 14.68 12.20 ZnO 2.85 1.640.00 0.00 2.98 0.00 0.00 MgO 0.03 0.03 3.09 2.08 1.00 0.03 0.03 SnO₂0.05 0.04 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.19 1.10 1.22 1.14 1.301.03 1.03 Li₂O/Na₂O 0.10 0.22 0.10 0.21 0.00 0.17 0.40 (R₂O + RO) −Al₂O₃ − P₂O₅ 3.05 0.70 3.61 1.72 5.40 −1.86 −1.92 Composition (mol %)Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 SiO₂ 63.89 63.92 63.7763.73 63.70 63.65 63.87 Al₂O₃ 16.55 15.29 15.27 15.30 15.27 15.22 15.29P₂O₅ 2.47 2.24 2.31 2.39 2.40 2.48 2.37 Li₂O 7.27 3.46 2.98 4.02 4.464.96 5.39 Na₂O 9.74 13.46 13.99 12.91 12.51 11.99 11.44 ZnO 0.00 1.561.61 1.57 1.58 1.63 1.57 MgO 0.03 0.02 0.02 0.03 0.03 0.02 0.02 SnO₂0.04 0.04 0.04 0.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.03 1.11 1.11 1.11 1.111.11 1.10 Li₂O/Na₂O 0.75 0.26 0.21 0.31 0.36 0.41 0.47 (R₂O + RO) −Al₂O₃ − P₂O₅ −1.98 0.97 1.01 0.84 0.90 0.91 0.76 Composition (mol %) Ex.36 Ex. 37 Ex. 38 Ex. 39 Ex. 40 Ex. 41 Ex. 42 SiO₂ 63.69 63.75 63.7063.62 63.74 63.77 63.77 Al₂O₃ 15.26 15.30 15.27 15.23 15.27 15.27 15.33P₂O₅ 2.45 2.42 2.45 2.46 2.47 2.46 2.44 Li₂O 2.96 2.98 3.94 3.98 4.934.93 2.91 Na₂O 13.50 13.46 12.54 12.57 11.49 11.50 13.94 ZnO 2.06 2.012.03 2.06 2.03 2.00 0.00 MgO 0.02 0.03 0.02 0.03 0.03 0.03 1.57 SnO₂0.05 0.04 0.04 0.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.08 1.08 1.08 1.09 1.081.08 1.10 Li₂O/Na₂O 0.22 0.22 0.31 0.32 0.43 0.43 0.21 (R₂O + RO) −Al₂O₃ − P₂O₅ 0.83 0.77 0.80 0.95 0.73 0.73 0.66 Composition (mol %) Ex.43 Ex. 44 Ex. 45 Ex. 46 Ex. 47 Ex. 48 Ex. 49 SiO₂ 63.69 63.81 63.6563.71 63.62 63.65 63.62 Al₂O₃ 15.25 15.26 15.33 15.32 15.24 15.68 15.67P₂O₅ 2.43 2.41 2.46 2.44 2.47 2.44 2.48 Li₂O 4.00 4.89 2.96 4.01 4.916.07 6.06 Na₂O 13.01 12.03 13.29 12.25 11.42 10.93 10.53 ZnO 0.00 0.002.24 2.20 2.27 1.17 1.57 MgO 1.57 1.56 0.03 0.03 0.02 0.02 0.02 SnO₂0.05 0.04 0.05 0.04 0.05 0.04 0.05 R₂O/Al₂O₃ 1.12 1.11 1.06 1.06 1.071.08 1.06 Li₂O/Na₂O 0.31 0.41 0.22 0.33 0.43 0.56 0.58 (R₂O + RO) −Al₂O₃ − P₂O₅ 0.90 0.81 0.73 0.73 0.91 0.08 0.04 Composition (mol %) Ex.50 Ex. 51 Ex. 52 Ex. 53 Ex. 54 Ex. 55 Ex. 56 SiO₂ 63.60 63.89 63.8463.90 63.88 64.74 60.17 Al₂O₃ 15.65 16.09 16.47 16.87 16.97 15.25 18.58P₂O₅ 2.46 2.42 2.43 2.43 2.42 0.98 1.90 Li₂O 6.13 6.80 7.84 8.75 9.785.28 5.16 Na₂O 10.29 9.97 8.96 7.99 6.88 12.09 12.58 ZnO 1.81 0.78 0.390.00 0.00 1.61 1.55 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02 SnO₂ 0.040.04 0.04 0.04 0.04 0.03 0.03 R₂O/Al₂O₃ 1.05 1.04 1.02 0.99 0.98 1.140.96 Li₂O/Na₂O 0.60 0.68 0.87 1.10 1.42 0.44 0.41 (R₂O + RO) − Al₂O₃ −P₂O₅ 0.14 −0.94 −1.68 −2.54 −2.70 2.78 −1.16 Composition (mol %) Ex. 57Ex. 58 Ex. 59 Ex. 60 Ex. 61 Ex. 62 Ex. 63 Ex. 64 SiO₂ 58.32 63.3 63.363.3 63.3 63.3 63.3 63.46 Al₂O₃ 18.95 15.25 15.65 16.2 15.1 15.425 15.715.71 P₂O₅ 2.42 2.5 2.5 2.5 2.5 2.5 2.5 2.45 Li₂O 4.96 6 7 7.5 6 7 7.56.37 Na₂O 13.74 10.7 9.7 9.45 10.55 9.475 8.95 10.69 ZnO 1.56 1.2 0.8 02.5 2.25 2 1.15 MgO 0.02 1 1 1 0 0 0 0.06 SnO₂ 0.03 0.05 0.05 0.05 0.050.05 0.05 0.04 R₂O/Al₂O₃ 0.99 1.10 1.07 1.05 1.10 1.07 1.05 1.09Li₂O/Na₂O 0.36 0.56 0.72 0.79 0.57 0.74 0.84 0.6 (R₂O + RO) − Al₂O₃ −P₂O₅ −1.09 1.15 0.35 −0.75 1.45 0.80 0.25 −1.1

TABLE 1B Selected physical properties of the glasses listed in Table 1B.Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Density (g/cm³) 2.434 2.4932.434 2.504 2.44 2.514 2.519 Low temperature CTE 8.9 8.62 8.95 8.6 8.828.71 8.54 25-300° C. (ppm/° C.) High temperature CTE (ppm/° C.) 17.6719.1 17.16 21 18.12 20 20.11 Strain pt. (° C.) 630 591 612 580 605 580589 Anneal pt. (° C.) 683 641 662 628 651 629 639 10¹¹ Poise temperature(° C.) 770 725 748 710 734 711 721 Softening pt. (° C.) 937 888 919 873909 868 874 T^(35 kP) (° C.) 1167 1180 1158 1160 T^(200 kP) (° C.) 10701083 1061 1064 Zircon breakdown 1205 1220 1170 1185 1205 temperature (°C.) Zircon breakdown viscosity (P) 1.56 × 10⁴ 4.15 × 10⁴ 2.29 × 10⁴ 1.74× 10⁴ Liquidus temperature (° C.) 980 990 975 990 1000 Liquidusviscosity (P) 1.15 × 10⁶ 2.17 × 10⁶ 9.39 × 10⁵ 7.92 × 10⁵ Poisson'sratio 0.200 0.211 0.206 0.214 0.204 0.209 0.211 Young's modulus (GPa)69.2 68.8 69.4 68.5 69.6 68.3 69.0 Refractive index at 589.3 nm 1.49761.5025 1.4981 1.5029 1.4992 1.5052 1.506 Stress optical coefficient2.963 3.158 3.013 3.198 2.97 3.185 3.234 (nm/mm/MPa) Ex. 8 Ex. 9 Ex. 10Ex. 11 Ex. 12 Ex. 13 Ex. 14 Density (g/cm³) 2.516 2.501 2.498 2.4932.493 2.492 2.486 Low temperature CTE 8.35 8.67 8.87 8.49 8.65 8.71 8.4925-300° C. (ppm/° C.) High temperature CTE (ppm/° C.) 20.11 20.6 20.9419.52 20.77 Strain pt. (° C.) 590 589 591 584 600 579 588 Anneal pt. (°C.) 641 639 640 628 652 620 630 10¹¹ Poise temperature (° C.) 726 724720 704 738 695 704 Softening pt. (° C.) 888 890 865 857 900 867 860T^(35 kP) (° C.) 1170 1176 1159 1139 1197 1169 T^(200 kP) (° C.) 10731080 1061 1041 1099 1070 Zircon breakdown 1195 1195 1210 1225 1195 11951220 temperature (° C.) Zircon breakdown viscosity (P) 2.33 × 10⁴ 2.58 ×10⁴ 1.60 × 10⁴ 9.94 × 10³ 3.63 × 10⁴ 2.35 × 10⁴ Liquidus temperature (°C.) 1005 990 990 980 990 980 980 Liquidus viscosity (P) 8.69 × 10⁴1.48E+06 9.02E+05 7.10E+05 2.19E+06 1.33E+06 Poisson's ratio 0.211 0.2050.208 0.209 0.209 0.210 0.217 Young's modulus (GPa) 69.0 68.7 71.4 73.568.4 71.6 74.0 Refractive index at 589.3 nm 1.506 1.5036 1.505 1.50631.5026 1.5041 1.5052 Stress optical coefficient 3.234 3.194 3.157 3.1313.18 3.156 3.131 (nm/mm/MPa) Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20Ex. 21 Density (g/cm³) 2.433 2.429 2.426 2.431 2.428 2.433 2.486 Lowtemperature CTE 9.15 9.16 8.83 8.97 8.97 8.79 8.45 25-300° C. (ppm/° C.)High temperature CTE (ppm/° C.) 20 20 21 17.3 20 Strain pt. (° C.) 615606 599 633 616 611 602 Anneal pt. (° C.) 662 659 653 684 670 665 65310¹¹ Poise temperature (° C.) 747 745 741 771 758 751 739 Softening pt.(° C.) 935 903 901 943 918 905 910 T^(35 kP) (° C.) 1182 1166 1152 12211185 1167 1207 T^(200 kP) (° C.) 1083 1066 1051 1122 1084 1066 1108Zircon breakdown temperature (° C.) Zircon breakdown viscosity (P)Liquidus temperature (° C.) Liquidus viscosity (P) Poisson's ratio 0.2030.207 0.205 0.209 0.199 0.207 Young's modulus (GPa) 68.9 71.2 72.7 69.470.9 68.1 Refractive index at 589.3 nm 1.4964 1.4981 1.4991 1.49651.4984 1.5006 1.5019 Stress optical coefficient 2.994 3.022 2.982 2.9792.99 0 3.173 (nm/mm/MPa) Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 Ex. 27 Ex.28 Density (g/cm³) 2.468 2.448 2.434 2.428 2.47 2.419 2.414 Lowtemperature CTE 8.6 8.23 8.91 8.25 8.66 8.52 8.17 25-300° C. (ppm/° C.)High temperature CTE (ppm/° C.) 19.52 19.49 19.47 Strain pt. (° C.) 596595 638 616 608 640 620 Anneal pt. (° C.) 644 649 695 656 654 700 67710¹¹ Poise temperature (° C.) 728 741 785 732 736 798 771 Softening pt.(° C.) 905 922 941 925 911 978 946 T^(35 kP) (° C.) 1217 1227 1209 12151209 1283 1249 T^(200 kP) (° C.) 1115 1125 1109 1115 1107 1184 1150Zircon breakdown 1185 1185 1180 1185 1185 temperature (° C.) Zirconbreakdown viscosity (P) 5.86E+04 6.91E+04 5.59E+04 5.72E+04 1.05E+05Liquidus temperature (° C.) 975 980 1080 1025 940 Liquidus viscosity (P)4.14E+06 4.52E+06 3.56E+05 1.27E+06 2.92E+07 Poisson's ratio 0.210 0.2040.210 0.212 0.213 Young's modulus (GPa) 71.4 71.6 73.5 68.8 76.9Refractive index at 589.3 nm 1.502 1.5025 1.4996 1.5008 1.5006 1.49871.5014 Stress optical coefficient 3.123 3.03 3.001 3.021 3.148 3.0393.015 (nm/mm/MPa) Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35Density (g/cm³) 2.408 2.446 2.448 2.446 2.445 2.443 2.442 Lowtemperature CTE 7.86 8.29 8.38 8.17 8.14 8.04 7.97 25-300° C. (ppm/° C.)High temperature CTE (ppm/° C.) 18.57 19.71 Strain pt. (° C.) 610 591595 585 580 574 577 Anneal pt. (° C.) 665 645 649 638 633 627 629 10¹¹Poise temperature (° C.) 755 736 740 726 722 717 717 Softening pt. (°C.) 924 915 919 894 894 895 890 T^(35 kP) (° C.) 1216 1223 1227 12161210 1203 1196 T^(200 kP) (° C.) 1120 1122 1126 1114 1108 1102 1095Zircon breakdown 1210 1175 1180 1190 1195 1210 1205 temperature (° C.)Zircon breakdown viscosity (P) 3.86E+04 7.72E+04 7.55E+04 5.29E+044.43E+04 3.14E+04 3.04E+04 Liquidus temperature (° C.) 1080 990 975 975975 975 980 Liquidus viscosity (P) 4.55E+05 3.28E+06 5.43E+06 3.80E+063.33E+06 3.02E+06 2.29E+06 Poisson's ratio 0.211 0.206 0.202 0.21 0.2040.204 0.203 Young's modulus (GPa) 75.0 73.91 73.02 74.60 74.67 75.1575.43 Refractive index at 589.3 nm 1.5053 1.503 1.5025 1.5035 1.50411.5046 1.5053 Stress optical coefficient 3.002 3.074 3.083 3.071 3.0593.016 3.053 (nm/mm/MPa) Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35Density (g/cm³) 2.408 2.446 2.448 2.446 2.445 2.443 2.442 Lowtemperature CTE 7.86 8.29 8.38 8.17 8.14 8.04 7.97 25-300° C. (ppm/° C.)High temperature CTE (ppm/° C.) 18.57 19.71 Strain pt. (° C.) 610 591595 585 580 574 577 Anneal pt. (° C.) 665 645 649 638 633 627 629 10¹¹Poise temperature (° C.) 755 736 740 726 722 717 717 Softening pt. (°C.) 924 915 919 894 894 895 890 T^(35 kP) (° C.) 1216 1223 1227 12161210 1203 1196 T^(200 kP) (° C.) 1120 1122 1126 1114 1108 1102 1095Zircon breakdown 1210 1175 1180 1190 1195 1210 1205 temperature (° C.)Zircon breakdown viscosity (P) 3.86E+04 7.72E+04 7.55E+04 5.29E+044.43E+04 3.14E+04 3.04E+04 Liquidus temperature (° C.) 1080 990 975 975975 975 980 Liquidus viscosity (P) 4.55E+05 3.28E+06 5.43E+06 3.80E+063.33E+06 3.02E+06 2.29E+06 Poisson's ratio 0.211 0.206 0.202 0.21 0.2040.204 0.203 Young's modulus (GPa) 75.0 73.91 73.02 74.60 74.67 75.1575.43 Refractive index at 589.3 nm 1.5053 1.503 1.5025 1.5035 1.50411.5046 1.5053 Stress optical coefficient 3.002 3.074 3.083 3.071 3.0593.016 3.053 (nm/mm/MPa) Ex. 36 Ex. 37 Ex. 38 Ex. 39 Ex. 40 Ex. 41 Ex. 42Density (g/cm³) 2.453 2.453 2.452 2.451 2.449 2.449 2.425 Lowtemperature CTE 8.17 8.14 7.97 8.01 7.79 7.9 8.54 25-300° C. (ppm/° C.)High temperature CTE (ppm/° C.) 20.56 Strain pt. (° C.) 595 595 584 587578 584 617 Anneal pt. (° C.) 649 649 638 640 630 637 663 10¹¹ Poisetemperature (° C.) 740 741 729 730 718 726 746 Softening pt. (° C.) 918921 905 907 894 901 929 T^(35 kP) (° C.) 1229 1232 1212 1219 1200 12041232 T^(200 kP) (° C.) 1128 1131 1111 1118 1100 1103 1132 Zirconbreakdown 1185 1200 1210 temperature (° C.) Zircon breakdown viscosity(P) 7.20E+04 4.26E+04 3.00E+04 Liquidus temperature (° C.) 995 990 965Liquidus viscosity (P) 3.33E+06 2.51E+06 3.71E+06 Poisson's ratio 0.2080.206 0.206 Young's modulus (GPa) 73.70 74.67 75.50 Refractive index at589.3 nm 1.5032 1.5042 1.5054 1.5005 Stress optical coefficient 3.0933.071 3.072 3.033 (nm/mm/MPa) Ex. 43 Ex. 44 Ex. 45 Ex. 46 Ex. 47 Ex. 48Ex. 49 Ex. 50 Density (g/cm³) 2.424 2.422 2.455 2.454 2.454 2.434 2.4392.443 Low temperature coefficient 8.48 8.34 8.03 7.88 7.76 7.87 7.717.63 of thermal expansion 25-300° C. (ppm/° C.) High temperaturecoefficient of thermal expansion (ppm/° C.) Strain pt. temperature (°C.) 614 594 595 586 579 580 581 579 Anneal pt. temperature (° C.) 659640 649 639 630 633 633 632 10¹¹ Poise temperature (° C.) 739 722 740729 718 722 721 721 Softening pt. temperature (° C.) 912 899 918 909 898892 893 895 35 kP temperature (° C.) 1216 1204 1212 1200 1203 1203 1203200 kP temperature (° C.) 1116 1102 1113 1099 1105 1102 1103 Zirconbreakdown temperature (° C.) Zircon breakdown viscosity (P) Liquidustemperature (° C.) 985 965 1005 1010 1030 Liquidus viscosity (P) 4.E+061.78E+06 1.34E+06 8.98E+05 Poisson's ratio 0.211 0.21 0.213 Young'smodulus (GPa) 76.32 76.60 76.81 Refractive index at 589.3 nm 1.50141.5026 1.5036 1.5047 1.5061 1.505 1.5059 1.5064 Stress opticalcoefficient 2.965 2.981 3.082 3.057 3.063 3.025 3.004 3.046 (nm/mm/MPa)Ex. 51 Ex. 52 Ex. 53 Ex. 54 Ex. 55 Ex. 56 Ex. 57 Density (g/cm³) 2.4242.431 2.403 2.4 2.45 2.462 2.468 Low temperature CTE 77.1 76.1 74.3 73.180.2 79.7 83.6 25-300° C. (ppm/° C.) High temperature CTE (ppm/° C.)Strain pt. (° C.) 588 599 611 612 580 611 597 Anneal pt. (° C.) 640 651665 665 631 663 649 10¹¹ Poise temperature (° C.) 728 738 753 752 718750 735 Softening pt. (° C.) 900.4 907.5 916 912.5 892.2 915.6 899.4T^(35 kP) (° C.) 1204 1209 1209 1202 1206 1205 1184 T^(200 kP) (° C.)1106 1113 1113 1106 1102 1111 1093 Zircon breakdown temperature (° C.)Zircon breakdown viscosity (P) Liquidus temperature (° C.) 1060 11151160 1205 Liquidus viscosity (P) 5.11E+05 1.90E+05 8.18E+04 3.32E+04Poisson's ratio 0.211 0.212 0.208 0.214 Young's modulus (GPa) 77.0178.05 77.57 78.74 Refractive index at 589.3 nm 1.5054 1.5055 1.50591.5072 Stress optical coefficient 3.011 2.98 2.982 2.964 (nm/mm/MPa) Ex.64 Density (g/cm³) 2.428 CTE 25-300° C. (ppm/° C.) 7.8 Strain pt. (° C.)571 Anneal pt. (° C.) 622 10¹¹ Poise temperature (° C.) Softening pt. (°C.) 881.4 T^(35 kP) (° C.) T^(200 kP) (° C.) 1645 Zircon breakdowntemperature (° C.) Zircon breakdown viscosity (P) Liquidus temperature(° C.) 1000 Liquidus viscosity (P) 1524280 Poisson's ratio 0.211 Young'smodulus (GPa) 76.3 Refractive index at 589.3 nm 1.51 Stress opticalcoefficient 3.02 (nm/mm/MPa)

Where the glass-based article includes a glass-ceramic, the crystalphases may include β-spodumene, rutile, gahnite or other known crystalphases and combinations thereof.

The glass-based article may be substantially planar, although otherembodiments may utilize a curved or otherwise shaped or sculptedsubstrate. In some instances, the glass-based article may have a 3D or2.5D shape. The glass-based article may be substantially opticallyclear, transparent and free from light scattering. The glass-basedarticle may have a refractive index in the range from about 1.45 toabout 1.55. As used herein, the refractive index values are with respectto a wavelength of 550 nm.

Additionally or alternatively, the thickness of the glass-based articlemay be constant along one or more dimension or may vary along one ormore of its dimensions for aesthetic and/or functional reasons. Forexample, the edges of the glass-based article may be thicker as comparedto more central regions of the glass-based article. The length, widthand thickness dimensions of the glass-based article may also varyaccording to the article application or use.

The glass-based article may be characterized by the manner in which itis formed. For instance, where the glass-based article may becharacterized as float-formable (i.e., formed by a float process),down-drawable and, in particular, fusion-formable or slot-drawable(i.e., formed by a down draw process such as a fusion draw process or aslot draw process).

A float-formable glass-based article may be characterized by smoothsurfaces and uniform thickness is made by floating molten glass on a bedof molten metal, typically tin. In an example process, molten glass thatis fed onto the surface of the molten tin bed forms a floating glassribbon. As the glass ribbon flows along the tin bath, the temperature isgradually decreased until the glass ribbon solidifies into a solidglass-based article that can be lifted from the tin onto rollers. Onceoff the bath, the glass glass-based article can be cooled further andannealed to reduce internal stress. Where the glass-based article is aglass ceramic, the glass-based article formed from the float process maybe subjected to a ceramming process by which one or more crystallinephases are generated.

Down-draw processes produce glass-based articles having a uniformthickness that possess relatively pristine surfaces. Because the averageflexural strength of the glass-based article is controlled by the amountand size of surface flaws, a pristine surface that has had minimalcontact has a higher initial strength. When this high strengthglass-based article is then further strengthened (e.g., chemically), theresultant strength can be higher than that of a glass-based article witha surface that has been lapped and polished. Down-drawn glass-basedarticles may be drawn to a thickness of less than about 2 mm. Inaddition, down drawn glass-based articles have a very flat, smoothsurface that can be used in its final application without costlygrinding and polishing. Where the glass-based article is a glassceramic, the glass-based article formed from the down draw process maybe subjected to a ceramming process by which one or more crystallinephases are generated.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glass-basedarticle. The fusion draw method offers the advantage that, because thetwo glass films flowing over the channel fuse together, neither of theoutside surfaces of the resulting glass-based article comes in contactwith any part of the apparatus. Thus, the surface properties of thefusion drawn glass-based article are not affected by such contact. Wherethe glass-based article is a glass ceramic, the glass-based articleformed from the fusion process may be subjected to a ceramming processby which one or more crystalline phases are generated.

The slot draw process is distinct from the fusion draw method. In slotdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous glass-based articleand into an annealing region.

The glass-based article may be acid polished or otherwise treated toremove or reduce the effect of surface flaws.

Another aspect of this disclosure pertains to devices that include theglass-based articles described herein. For example, the devices mayinclude any device including a display or requiring, strengthened thinglass. In one or more embodiments the devices are electronic devices,which can include mobile devices such as mobile phones, laptops,tablets, mp3 players, navigation devices and the like, or stationarydevices such as computers, electronic displays, in vehicleinformation/entertainment systems, billboards, point of sale systems,navigation systems, and the like). In some embodiments, the glass-basedarticles described herein may be incorporated into architecturalarticles (walls, fixtures, panels, windows, etc.), transportationarticles (e.g., glazing or interior surfaces in automotive applications,trains, aircraft, sea craft, etc.), appliances (e.g., washers, dryers,dishwashers, refrigerators and the like), or any article that requiressome fracture resistance. As shown in FIG. 28, an electronic device 1000may include a glass-based article 100 according to one or moreembodiments described herein. The device 100 includes a housing 1020having front 1040, back 1060, and side surfaces 1080; electricalcomponents (not shown) that are at least partially inside or entirelywithin the housing and including at least a controller, a memory, and adisplay 1120 at or adjacent to the front surface of the housing. Theglass-based article 100 is shown as a cover disposed at or over thefront surface of the housing such that it is over the display 1120. Insome embodiments, the glass-based article may be used as a back cover.

Another aspect of this disclosure pertains to a method of forming afracture-resistant glass-based article. The method includes providing aglass-based substrate having a first surface and a second surfacedefining a thickness of about 1 millimeter or less and generating astress profile in the glass-based substrate, as described herein toprovide the fracture-resistant glass-based article. In one or moreembodiments, generating the stress profile comprises ion exchanging aplurality of alkali ions into the glass-based substrate to form anon-zero alkali metal oxide concentration that varies along asubstantial portion of the thickness (as described herein) or along theentire thickness. In one example, generating the stress profile includesimmersing the glass-based substrate in a molten salt bath includingnitrates of Na+, K+, Rb+, Cs+ or a combination thereof, having atemperature of about 350° C. or greater (e.g., about 350° C. to about500° C.). In one example, the molten bath may include NaNO₃, KNO₃ or acombination thereof, and may have a temperature of about 485° C. orless. In another example, the bath may include a mixture of NaNO₃ andKNO₃ and have a temperature of about 460° C. The glass-based substratemay be immersed in the bath for about 2 hours or more, up to about 48hours (e.g., from about 2 hours to about 10 hours, from about 2 hours toabout 8 hours, from about 2 hours to about 6 hours, from about 3 hoursto about 10 hours, or from about 3.5 hours to about 10 hours).

In some embodiments, the method may include chemically strengthening orion exchanging the glass-based substrate in a single bath or in morethan one step using successive immersion steps in more than one bath.For example, two or more baths may be used successively. The compositionof the one or more baths may include a single metal (e.g., Ag+, Na+, K+,Rb+, or Cs+) or a combination of metals in the same bath. When more thanone bath is utilized, the baths may have the same or differentcomposition and/or temperature as one another. The immersion times ineach such bath may be the same or may vary to provide the desired stressprofile.

In one or more embodiments of the method, a second bath or subsequentbaths may be utilized to generate a greater surface CS. In someinstances, the method includes immersing the glass-based substrate inthe second or subsequent baths to generate a greater surface CS, withoutsignificantly influencing the chemical depth of layer and/or the DOC. Insuch embodiments, the second or subsequent bath may include a singlemetal (e.g., KNO₃ or NaNO₃) or a mixture of metals (KNO₃ and NaNO₃). Thetemperature of the second or subsequent bath may be tailored to generatethe greater surface CS. In some embodiments, the immersion time of theglass-based substrate in the second or subsequent bath may also betailored to generate a greater surface CS without influencing thechemical depth of layer and/or the DOC. For example, the immersion timein the second or subsequent baths may be less than 10 hours (e.g., about8 hours or less, about 5 hours or less, about 4 hours or less, about 2hours or less, about 1 hour or less, about 30 minutes or less, about 15minutes or less, or about 10 minutes or less).

In one or more alternative embodiments, the method may include one ormore heat treatment steps which may be used in combination with theion-exchanging processes described herein. The heat treatment includesheat treating the glass-based article to obtain a desired stressprofile. In some embodiments, heat treating includes annealing,tempering or heating the glass-based substrate to a temperature in therange from about 300° C. to about 600° C. The heat treatment may lastfor 1 minute up to about 18 hours. In some embodiments, the heattreatment may be used after one or more ion-exchanging processes, orbetween ion-exchanging processes.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment, a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) (mm); a concentration of a metal oxidethat is both non-zero and varies along a thickness range from about 0·tto about 0.3·t; and a central tension (CT) region comprising a maximumCT (MPa) of less than about 71.5/√(t), wherein the article exhibits athreshold failure impact force greater than 500 Newtons when the articleis bent to impart a tensile stress of 100 MPa. In one or more specificembodiments, the glass article exhibits a threshold failure impact forcegreater than 525, 550, 575, 600, 625, 650, 675, 700, 725, 750, 775, 800,825 or 800 Newtons when the article is bent to impart a tensile stressof 100 MPa. According to one or more embodiments, the glass-basedarticle having the aforementioned threshold failure impact forceproperties has a thickness in the range of 0.1 to 3 mm, moreparticularly, 0.2 to 2 mm, 0.2 to 1.9 mm, 0.2 to 1.8 mm, 0.2 to 1.7 mm,0.2 to 1.6 mm, 0.2 to 1.5 mm, 0.2 to 1.4 mm, 0.2 to 1.3 mm, 0.2 to 1.2mm, 0.2 to 1.1 mm, 0.3 to 1 mm, 0.3 to 0.9 mm, 0.3 to 0.8 mm, 0.3 to 0.7mm, 0.3 to 0.6 mm, 0.3 to 0.5 mm and 0.3 to 0.4 mm. In specificembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness of 0.4 mm, 0.5, mm, 0.6,mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5mm, 1.6 mm, 1.7 mm, 1.8 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3 mm. In any of theabove-described embodiments, the glass-based article having theaforementioned threshold failure impact force properties and thicknesseshas a surface compressive stress of greater than about 200 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) (mm); a concentration of a metal oxidethat is both non-zero and varies along a thickness range from about 0·tto about 0.3·t; and a central tension (CT) region comprising a maximumCT (MPa) of less than about 71.5/√(t), wherein the article exhibits aretained strength of 125 MPa or more after being impacted by an impactforce of 800 N when the article is bent to impart a tensile stress of100 MPa. In one or more embodiments, the glass based article exhibits aretained strength of 135, 145, 150, 160, 170, 180, 190 or 200 or moreMPa after being impacted by an impact force of 800 N when the article isbent to impart a tensile stress of 100 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) of about less than about 3 millimeters;and a stress profile extending along the thickness, wherein all pointsof the stress profile between a thickness range from about 0·t up to0.3·t and from greater than 0.7·t, comprise a tangent with a slopehaving an absolute value that is greater than about 0.1 MPa/micrometer,wherein the stress profile comprises a maximum CS, a DOC and a maximumCT of less than about 71.5/√(t) (MPa), wherein the ratio of maximum CTto absolute value of maximum CS is in the range from about 0.01 to about0.2 and wherein the DOC is about 0.1·t or greater, and wherein thearticle exhibits a threshold failure impact force greater than 500Newtons when the article is bent to impart a tensile stress of 100 MPa.

In one or more specific embodiments, the glass article exhibits athreshold failure impact force greater than 525, 550, 575, 600, 625,650, 675, 700, 725, 750, 775, 800, 825 or 800 Newtons when the articleis bent to impart a tensile stress of 100 MPa. According to one or moreembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness in the range of 0.1 to 3mm, more particularly, 0.2 to 2 mm, 0.2 to 1.9 mm, 0.2 to 1.8 mm, 0.2 to1.7 mm, 0.2 to 1.6 mm, 0.2 to 1.5 mm, 0.2 to 1.4 mm, 0.2 to 1.3 mm, 0.2to 1.2 mm, 0.2 to 1.1 mm, 0.3 to 1 mm, 0.3 to 0.9 mm, 0.3 to 0.8 mm, 0.3to 0.7 mm, 0.3 to 0.6 mm, 0.3 to 0.5 mm and 0.3 to 0.4 mm. In specificembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness of 0.4 mm, 0.5, mm, 0.6,mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm 1.5 mm,1.6 mm, 1.7 mm, 1.8 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm,2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3 mm. In any of the above-describedembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties and thicknesses has a surfacecompressive stress of greater than about 200 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) of about less than about 3 millimeters;and a stress profile extending along the thickness, wherein all pointsof the stress profile between a thickness range from about 0·t up to0.3·t and from greater than 0.7·t, comprise a tangent with a slopehaving an absolute value that is greater than about 0.1 MPa/micrometer,wherein the stress profile comprises a maximum CS, a DOC and a maximumCT of less than about 71.5/√(t) (MPa), wherein the ratio of maximum CTto absolute value of maximum CS is in the range from about 0.01 to about0.2 and wherein the DOC is about 0.1·t or greater, and wherein thearticle exhibits a retained strength of 125 MPa or more after beingimpacted by an impact force of 800 N when the article is bent to imparta tensile stress of 100 MPa. In one or more embodiments, the glass basedarticle exhibits a retained strength of 135, 145, 150, 160, 170, 180,190 or 200 or more MPa after being impacted by an impact force of 800 Nwhen the article is bent to impart a tensile stress of 100 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) (mm); and a metal oxide that forms aconcentration gradient, wherein the concentration of the metal oxidedecreases from the first surface to a point between the first surfaceand the second surface and increases from the point to the secondsurface, wherein the concentration of the metal oxide at the point isnon-zero, and wherein the article exhibits a threshold failure impactforce greater than 500 Newtons when the article is bent to impart atensile stress of 100 MPa.

In one or more specific embodiments, the glass article exhibits athreshold failure impact force greater than 525, 550, 575, 600, 625,650, 675, 700, 725, 750, 775, 800, 825 or 800 Newtons when the articleis bent to impart a tensile stress of 100 MPa. According to one or moreembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness in the range of 0.1 to 3mm, more particularly, 0.2 to 2 mm, 0.2 to 1.9 mm, 0.2 to 1.8 mm, 0.2 to1.7 mm, 0.2 to 1.6 mm, 0.2 to 1.5 mm, 0.2 to 1.4 mm, 0.2 to 1.3 mm, 0.2to 1.2 mm, 0.2 to 1.1 mm, 0.3 to 1 mm, 0.3 to 0.9 mm, 0.3 to 0.8 mm, 0.3to 0.7 mm, 0.3 to 0.6 mm, 0.3 to 0.5 mm and 0.3 to 0.4 mm. In specificembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness of 0.4 mm, 0.5, mm, 0.6,mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5mm, 1.6 mm, 1.7 mm, 1.8 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3 mm. In any of theabove-described embodiments, the glass-based article having theaforementioned threshold failure impact force properties and thicknesseshas a surface compressive stress of greater than about 200 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a first surface and a second surface opposing the firstsurface defining a thickness (t) (mm); and a metal oxide that forms aconcentration gradient, wherein the concentration of the metal oxidedecreases from the first surface to a point between the first surfaceand the second surface and increases from the point to the secondsurface, wherein the concentration of the metal oxide at the point isnon-zero, and wherein the article exhibits a retained strength of 125MPa or more after being impacted by an impact force of 800 N when thearticle is bent to impart a tensile stress of 100 MPa. In one or moreembodiments, the glass based article exhibits a retained strength of135, 145, 150, 160, 170, 180, 190 or 200 or more MPa after beingimpacted by an impact force of 800 N when the article is bent to imparta tensile stress of 100 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a stress profile including a CS region and a CT region,wherein the CT region is approximated by the equationStress(x)=MaxT−(((CT_(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(n)), wherein MaxTis a maximum tension value and is a positive value in units of MPa,wherein CT_(n) is the tension value at n, CT_(n) is less than or equalto MaxT, and is a positive value in units of MPa, wherein x is positionalong the thickness (t) in micrometers, wherein n is in the range from1.5 to 5, and wherein the article exhibits a threshold failure impactforce greater than 500 Newtons when the article is bent to impart atensile stress of 100 MPa.

In one or more specific embodiments, the glass article exhibits athreshold failure impact force greater than 525, 550, 575, 600, 625,650, 675, 700, 725, 750, 775, 800, 825 or 800 Newtons when the articleis bent to impart a tensile stress of 100 MPa. According to one or moreembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness in the range of 0.1 to 3mm, more particularly, 0.2 to 2 mm, 0.2 to 1.9 mm, 0.2 to 1.8 mm, 0.2 to1.7 mm, 0.2 to 1.6 mm, 0.2 to 1.5 mm, 0.2 to 1.4 mm, 0.2 to 1.3 mm, 0.2to 1.2 mm, 0.2 to 1.1 mm, 0.3 to 1 mm, 0.3 to 0.9 mm, 0.3 to 0.8 mm, 0.3to 0.7 mm, 0.3 to 0.6 mm, 0.3 to 0.5 mm and 0.3 to 0.4 mm. In specificembodiments, the glass-based article having the aforementioned thresholdfailure impact force properties has a thickness of 0.4 mm, 0.5, mm, 0.6,mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5mm, 1.6 mm, 1.7 mm, 1.8 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3 mm. In any of theabove-described embodiments, the glass-based article having theaforementioned threshold failure impact force properties and thicknesseshas a surface compressive stress of greater than about 200 MPa.

One or more embodiments of glass compositions described herein can beused to make glass-based articles as described herein, includingExamples 1-64 above and Examples 1-6 below, as well as the ranges ofcompositions described herein. In one embodiment a glass-based articlecomprises a stress profile including a CS region and a CT region,wherein the CT region is approximated by the equationStress(x)=MaxT−(((CT_(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(n)), wherein MaxTis a maximum tension value and is a positive value in units of MPa,wherein CT_(n) is the tension value at n, CT_(n) is less than or equalto MaxT, and is a positive value in units of MPa, wherein x is positionalong the thickness (t) in micrometers, wherein n is in the range from1.5 to 5, and wherein the article exhibits a retained strength of 125MPa or more after being impacted by an impact force of 800 N when thearticle is bent to impart a tensile stress of 100 MPa. In one or moreembodiments, the glass based article exhibits a retained strength of135, 145, 150, 160, 170, 180, 190 or 200 or more MPa after beingimpacted by an impact force of 800 N when the article is bent to imparta tensile stress of 100 MPa.

In the embodiments described immediately above which include thematerial property that article exhibits a threshold failure impact forcegreater than a certain force value when the article is bent to impart atensile stress of 100 MPa or certain a retained strength of a certainvalue (or more) after being impacted by an impact force of 800 N whenthe article is bent to impart a tensile stress of 100 MPa, theseproperties can be tested as follows. According to one or moreembodiments, “threshold failure impact force” refers to the minimumimpact force that is sufficient to causes an observable fracture on thesurface of the article, as described above with respect to FIG. 8. Inone or more embodiments, the article tested for “threshold failureimpact force” is a sheet having a thickness of 0.1 mm, 0.2 mm, 0.3 mm,0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm,1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2 mm.

Retained strength is measured by using a four point bend test (asdescribed herein) or an AROR test as described herein. The phrase “whenthe article is bent to impart a tensile stress of 100 MPa” refers to anexternally applied tensile stress to a glass based article that is theresult of bending. Thus, when a glass-based article is bent, forming anapex that is a contact surface according to the testing describedherein, apex, which is at the outer surface of the glass-based articlewhen it is bent, has an externally applied tensile stress as a result ofthe bending.

Additional aspects of the disclosure relate to apparatus and methods formeasuring threshold failure impact force. Reliability testing of devicesis integral to understanding how they will perform during theirapplication lifetime. Device drop testing is commonly employed tounderstand handheld electronic device (e.g. smartphone, tablets,laptops, etc.) reliability after incurring drop events (e.g. dropping aphone in a parking lot), as these events could compromise the devicefunctionality. One concern with devices is the reliability of the coverglass used in these devices. Damage or fracture to the cover glass of ahandheld, electronic device can result in a non-useable device and/orsafety issues for the user. Understanding the limitation of the covermaterial and how it relates to the device design is integral toimproving cover glass performance.

Typically, real devices are drop tested to understand their reliability.However, this can become very expensive and is only available when thedevice design has become finalized and devices have been fabricated. Tohandle these drawbacks, surrogate test vehicles (reusable, mock-up ofdevices that resemble device dimensions and weight) are used to simulatedevice for cover glass performance testing. These surrogate vehicleshelp in understanding the capability of the glass to meet customerrequirements and help in providing design feedback that aids in coverglass survivability (e.g. bevel design). However, the building of thesurrogate vehicles and to performing the (drop) test is time consumingand quite expensive. Thus, it would be desirable to provide a less timeconsuming and inexpensive test on the concept of damage introduction andbending, as seen in most field failure mode.

An aspect of the disclosure pertains to an apparatus for testing surfaceof a glass-based article, for example, a cover glass for mobileelectronic devices such that it simulates a failure mode that has beenobserved to occur in the field, which is predominantly a combination ofstress (bending) and damage introduction. This known failure mode isre-created using a component-level based surface impact test. Extensivetesting has been conducted using this apparatus and it has been learnedthat certain glass compositions and ion exchange stress profiles canimprove cover glass survivability, through this test.

In one or more embodiments, the apparatus comprises a simplependulum-based dynamic impact test having a surface ranging from flat tocurved, where the glass-based article test specimen is mounted to a bobof a pendulum, which is then used to cause the test specimen to contactan impact surface, which can be a smooth or roughened surface. In one ormore embodiments, to perform the test, the sample is loaded on theholder and then pulled backwards from the pendulum equilibrium positionand released to make a dynamic impact on the impact surface. The testmimics a drop event, such that the glass/specimen is the moving part andthe surface is the stationary part. Available curved surfaces are asimulative of stress numbers (bending stress) obtained from fieldfailures. According to one or more embodiments of the apparatus, theglass-based article is the moving part, which travels to strike theimpact surface, which is the stationary part, replicative of a device(moving part) dropped from a given height onto a surface (stationarypart).

Failure mode is known to vary with the speed of damage introduction andbending rate. Unlike other quasi-statistic load application basedcomponent-level test, such as ring-on-ring (ROR), indentation fracturethreshold (IFT) and abraded ring-on-ring (ARoR—which involves damageintroduction followed by slow bending through quasi-static loadapplication) used to characterize cover glass performance, this test isdynamic in nature. Furthermore, with the increasing demand for thincover material in mobile device applications becoming very popular, theneed to have a component level based test to evaluate different thincover materials becomes important. This test can be used in theprediction of the potential drop performance response of this thinglass, as it demonstrated credibility in the evaluation of glassmaterials, of different compositions and IOX treatments, as low as 0.3mm thickness. According to one or more embodiments, the test methodsimplicity enables quicker estimation of glass impact energy andassociated impact force, which compares well to those generated fromsystem level drop test.

Referring now to FIGS. 29-33, an embodiment of an apparatus 1100 forimpact testing a brittle substrate is shown as comprising a pendulum1102 including a bob 1104 attached to a pivot 1106. A bob on a pendulumis a weight suspended from the pivot and connected to a pivot by an arm.Thus, the bob 1104 shown in the Figures is connected to the pivot 1106by arm 1108, which may be in the form of a string, or a rod or aplurality of rods, such as two rods as shown. As best shown in FIG. 33,the bob 1104 has an equilibrium position 1105 shown as dotted line suchthat the angle β is zero. In other words, the arm 1108 is not in araised position.

The bob 1104 can simply be the brittle substrate that is affixed to thelower end of the arm 1108. In one or more embodiments, the bob 1104includes a base 1110 for receiving a brittle substrate. As shown inbetter detail in FIG. 34, the base 1110 for receiving a brittlesubstrate 1112 having at least two ends 1114, 1116, an inner surface1113 and an outer surface 1115. The base 1110 has a first end 1120 and asecond end 1122, and a curved surface 1124 defining a radius ofcurvature between the first end 1120 and the second end 1122. The base1110 can be any suitable material to provide a platform to secure asubstrate for the impact test, which will be described further below.Suitable materials for the base 1110 can include wood, metal, ceramic,or combinations thereof. The curved surface 1124 has an apex 1125.

The apparatus 1100 according to one or more embodiments further includesa first fixture 1130 and a second fixture 1132 to hold the at least twoends 1114, 1116 of the brittle substrate 1112 and to apply a force tobend the brittle substrate 1112 about the curved surface 1124 and toconform the brittle substrate to the radius of curvature. By bending thebrittle substrate 1112, the brittle substrate has an apex 1127conforming to the apex 1125 of the curved surface 1124. In one or morespecific embodiments, the curved surface 1124 and the curvature of thebrittle substrate 1112 can be a fixed radius or a compound radius. Thefirst fixture 1130 and the second fixture 1132 each are a clamp, and inspecific embodiments toggle clamps as shown in FIG. 34. However, othertypes of fixtures such as bar clamps, C-clamps, or other suitablefixtures to hold the ends of the brittle substrate can be used.

The apparatus 1100 according to one or more embodiments further includesa roughened surface, which can be an abrasive sheet having an abrasivesurface to be placed in contact with the outer surface 1115 of thesubstrate 1112. The abrasive sheet is attached to impact surface 1150(of impacting object 1140 described below) by double sided tape, withthe abrasive surface of the abrasive sheet facing toward the curvedsurface 1124 on which the substrate 1112 is mounted. In other specificembodiments, the abrasive sheet comprises sandpaper, which may have agrit size in the range of 30 grit to 400 grit, or 100 grit to 300 grit,for example 180 grit. One suitable sandpaper is Indasa Rhynowet® PlusLine P180 grit sandpaper. The sandpaper according to one or moreembodiments is cut in 25 mm square pieces, and the sandpaper isflattened if the pieces are bent during the cutting process.

The apparatus 1100 further includes an impacting object 1140 positionedsuch that when the bob 1104 is released from a position at an angle βgreater than zero from the equilibrium position 1105, the curved surface1124 of the bob 1104 (or a substrate 1112 mounted on the curved surface1124) contacts the impact surface 1150 (or the abrasive side of anabrasive sheet disposed on the impact surface 1150) of the impactingobject 1140. In the embodiment shown, the impacting object 1140 is aL-shaped bracket affixed to platform 1142, and the impacting object 1140is affixed to the platform 1142 by screw 1144. The impacting object 1140could also be affixed by any other suitable mechanism such as a bolt,rivet, clamp, etc. The platform 1142 includes a stopper 1146, whichpermits the apparatus 1100 to be held at the end of work bench 1148. Inthe embodiment shown, the impacting object 1140 is fixed and does notmove when the bob 1104 contacts the impacting object 1140 at impactsurface 1150. The impact surface 1150 may be a separate element that ismovable in the x-y plane as best seen in FIG. 32 within slot 1152.Alternatively, the impact surface 1150 need not move relative to theimpacting object 1140. In one or more embodiments, the bob 1104 and base1110 are sized and shaped such that when a brittle substrate is affixedto the base 1110 and when the bob 1104 is released from a position at anangle β greater than zero from the equilibrium position 1105, thebrittle substrate 1112 is subjected to a bending radius and an impactforce that simulate a bending radius of a chemically strengthened coverglass of a mobile phone or tablet device when the mobile phone or tabletdevice is dropped on a ground surface by a user of the mobile phone ortablet device.

In one or more embodiments the radius of curvature of the curved surface1124 on the base 1110 is selected to provide a bending tensile force of100 MPa when a substrate is bent around the curved surface 1124 suchthat the tensile force is an externally applied tensile force thatresults from the stress of bending the substrate. Thus, when thesubstrate is bent, the tensile force is at the apex 1125 of the brittlesubstrate. According to one or more embodiments, the radius of curvatureis in the range of 0.25 m and 1.5 m, for example, in the range of 0.5 mand 1 m.

In one or more embodiments, the first fixture 1130 and second fixture1132 are spaced apart at a distance of a cover glass length for a mobilephone or a tablet. In specific embodiments, the first fixture 1130 andsecond fixture 1132 are spaced apart at a distance in the range of 50 mmand 500 mm.

Another aspect of the disclosure pertains to a method of impact testinga brittle sheet, the method comprising: bending the brittle sheet havinga contact surface to provide a bent sheet having a radius of curvatureand an apex on the contact surface; and impacting the bent sheet at theapex with an impacting object using a pendulum. In an embodiment, thebent sheet is attached to a pendulum bob. In an embodiment, the bentsheet attached to a pendulum bob is positioned such that the impactingobject contacts the apex of the contact surface. In one or moreembodiments, the brittle sheet is glass and the radius of curvature isin a range that simulates a bending radius of a chemically or thermallystrengthened cover glass of a mobile phone or tablet device when themobile phone or tablet device is dropped on a ground surface by a userof the mobile phone or tablet device, wherein the drop event is suchthat an edge of the device contacts the ground first (as opposed to aface first drop wherein the device generally hits the ground in anorientation such that the contact surface is generally parallel to theground).

In one or more embodiments, an abrasive sheet is placed on the impactsurface 1150 in a position so as to contact the apex of the brittlesheet upon a swinging movement of the arm 1108. In one or moreembodiments, the brittle sheet is secured to the impacting object withdouble sided tape.

Another embodiment pertains to a method of impact testing a brittlesheet, the method comprising: attaching a brittle sheet to a pendulumbob to expose a contact surface on the brittle sheet; and moving thependulum bob with the brittle sheet attached to the pendulum bob tocause the contact surface to contact an impact object. In an embodiment,the method includes bending the brittle sheet to provide a bent sheethaving a radius of curvature and an apex on the contact surface. In anembodiment, the bent sheet attached to a pendulum bob is positioned suchthat the impact object contacts the apex of the contact surface. In oneor more embodiments, the brittle sheet is glass and the radius ofcurvature is in a range that simulates a bending radius of a chemicallyor thermally strengthened cover glass of a mobile phone or tablet devicewhen the mobile phone or tablet device is dropped on a ground surface bya user of the mobile phone or tablet device, wherein the drop event issuch that an edge of the device contacts the ground first (as opposed toa face first drop wherein the device generally hits the ground in anorientation such that the contact surface is generally parallel to theground). In some embodiments, the brittle sheet is secured to a curvedsurface prior to impacting the apex with the impacting object.

Referring now to FIGS. 29 and 30, specific, non-limiting details ofoperation of the apparatus include a pointer notch 1200 on the pivot1106, which can point to various test positions 1202, i.e., positions atwhich the arm 1108 is positioned at angle β relative to equilibriumposition 1105, and positions from which motion of the pendulum isinitiated. The pointer notch 1200 enables alignment with a variety oftest positions 1202, which may be any suitable number of test positions,for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and so on incrementally up to50 or more. The apparatus 1100 may further include a lock, which may bein the form of nut 1204 to lock the arm 1108 in the desired rotationalorientation about its central longitudinal axis so as to square the base1110 with the impact surface 1150 of the impacting object 1140.

The apparatus 1100 simulates an actual phone drop event according to oneor more embodiments. Incident impact energy, E and average impact force,{right arrow over (F)}_(avg) are provided by the equations

$\begin{matrix}{E = {m\; g\; L\left\{ {1 - {\cos \; \beta}} \right\}}} \\{{{\overset{\rightarrow}{F}}_{avg}} = {\frac{{{m{\overset{\rightarrow}{v}}_{f}} - {m{\overset{\rightarrow}{v}}_{i}}}}{\Delta \; t}\quad}}\end{matrix}\quad$

Where, m=mass of the pendulum 1102 (including swing arm 1108, bob 1104,and base 1110), L=length of arm, g=acceleration of free fall, vj is theinitial impact velocity (i.e., the velocity at the point when the glassfirst contacts the impact surface 1150 of the impacting object 1140),and vi is the final impact velocity (i.e., the velocity at which theglass leaves the impact surface 1150 of the impacting object 1140, or inother words at the point when the glass first separates from the impactsurface 1150 of the impacting object 1140), and Δt=contact interactiontime (i.e., the time during which the glass is in contact with theimpact surface 1150 of the impacting object 1140). The contactinteraction time is measured by high-speed video camera by observing thenumber of frames during which the glass is in contact with the impactsurface 1150, and multiplying by the number of frames taken per unittime by the high-speed video camera. The average force equation isuseful for samples that have not been broken already, i.e., the samplesloaded into the apparatus 1100 prior to the test are ones that have notalready been broken. When the mass and length of the swing arm areknown, setting the angle β to a selected position, an impact force canbe calculated and used to simulate impacts on a device when dropped froma specific height. For example, the average force experienced by asubstrate cover glass on a 130 g mobile phone device when dropped from 1meter height has been calculated to be 800 N. Using the mass, arm lengthand angle β, this force can be replicated using the apparatus 1100 shownin FIGS. 29-34.

Referring to FIG. 35, the point 1500 on the graph represents the failurethreshold force for an alternative aluminosilicate glass substratehaving a thickness of 0.5 mm that was tested on the apparatus shown inFIGS. 29-33. FIG. 35 shows the swing angle as correlated to the averageimpact force. The alternative aluminosilicate glass had a failurethreshold force of about 200 Newtons. Point 1504 is for a 0.5 mm thickglass substrate having a nominal composition of 57.5 mol % SiO₂, 16.5mol % Al₂O₃, 16.5 mol % Na₂O, 2.8 mol % MgO, 6.5 mol % P₂O₅, and 0.05mol % SnO₂. The glass substrate from this test (at point 1504) had afailure threshold of less than 500 Newtons. Data for glass substratesmanufactured according to the glass articles claimed herein and madeaccording to Examples 1-64 above and Examples 1-6 below is shown aspoint 1506 and having an impact force exceeding 800 N. These values areplotted on FIG. 36, along with another chemically strengthened glass,labeled as ALT2. As indicated in FIG. 36, all glass substrates weretested with the pendulum apparatus 1100 described with respect to FIGS.29-34, with the bend radius at 0.4 mm to impart an externally appliedtensile stress by bending on the apex of the glass substrate of 100 MPa.

After the pendulum apparatus test was conducted on various samples, thesamples were tested for strength, which is referred to on FIG. 37 as“Retained Strength”, which refers to the strength of the substrate afterbeing impacted by an impact force as specified when the article is bentto impart a tensile stress of 100 MPa. The retained strength values weremeasured using the four point bend test as described herein. In FIG. 37,the vertical dotted line represents an impact force of 800 N, and theimpact forces to test samples were normalized on the x-axis. The ALT(alternative aluminosilicate glass substrates—diamond data points) hadthe worst retained strength values and could not be tested at the impactforce of 800 N, as all parts failed at much lower impact forces. TheALT2 (triangle data points) glass substrates impacted with an impactforce of 800 N did not have a retained strength greater than 125 N.However, glass substrates manufactured according to the glass articlesclaimed herein and made according to Examples 1-64 above and Examples1-6 below is shown as 1506 (square data points) all had retainedstrength values exceeding 125 MPa, namely greater than 150 MPa, and somegreater than 200 MPa.

EXAMPLES

Various embodiments will be further clarified by the following examples.In the Examples, prior to being strengthened, the Examples are referredto as “substrates”. After being subjected to strengthening, the Examplesare referred to as “articles” or “glass-based articles”.

Example 1

Examples 1A-1G included glass substrates having a nominal composition ofabout 63.46 mol % SiO₂, 15.71 mol % Al₂O₃, 6.37 mol % Li₂O, 10.69 mol %Na₂O, 0.06 mol % MgO, 1.15 mol % ZnO, 2.45 mol % P₂O₅, and 0.04 mol %SnO₂. The glass substrates had a thickness of 0.8 mm. The glasssubstrates of Examples 1A-1G were ion exchanged in a molten salt bathincluding 100% NaNO₃ and having a temperature of about 390° C.,according to the conditions in Table 2. The resulting glass-basedarticles exhibited maximum CT values, which are plotted as a function ofion exchange time in FIG. 10.

TABLE 2 Ion exchange conditions for Examples 1A-1G. Time immersed inExample bath (hours) Maximum CT 1A 0.5 30 1B 1 42 1C 1.5 52 1D 2 56 1E3.75 67 1F 8 63 1G 16 55

The stress profile for Example 1E was measured using the RNF method, asdescribed herein. FIG. 11 shows the measured stress as a function ofdepth extending from the surface of the glass-based article of Example1E into the glass-based article. The stress at specific depths is shownin Table 3, including at the “knee” which is the depth at which theslope of the stress changes drastically. In FIG. 11, positive numbersare used for compressive stress, and negative numbers indicate tensilestress. This same convention (compressive stress is indicated aspositive values on the y axis, and tensile stress is indicated bynegative values on the y axis) is used for FIGS. 1-3 also. However, inthe remainder of the figures, compressive stress is indicated asnegative values on the y axis and tensile stress is indicated aspositive values on the y axis.

TABLE 3 Stress at specific depths of Example 1E. Depth (micrometers)Stress (MPa) 12 (“knee”) 161  50 95 100 36 150 0

Example 2

Example 2A included a glass substrate having the same composition asExample 1 and a thickness of 0.8 mm. The glass substrate was ionexchanged in a single molten salt bath including 51% KNO3 and 49% NaNO₃,and having a temperature of about 380° C., for 3.75 hours. The resultingglass-based article exhibited the stress profile as described in Table4.

TABLE 4 Stress profile of Example 2A. Surface Compressive 500 MPa StressPotassium DOL for 12 micrometers potassium Stress at potassium DOL 161MPa of potassium Maximum CT 70 MPa DOC 150 micrometers

Glass-based articles according to Example 2A were subjected to ARORtesting as described herein. One set of glass-based articles was abradedusing a load or pressure of 5 psi, a second set of glass-based articleswas abraded using a load or pressure of 25 psi, and a third set ofglass-based articles was abraded using a load or pressure of 45 psi. TheAROR data is shown in FIG. 12. As shown in FIG. 12, all of theglass-based articles according to Example 2A exhibited an average loadto failure of greater than about 20 kgf

Glass-based articles according to Example 2A were retrofitted ontoidentical mobile phone devices. The phone devices were dropped fromincremental heights starting at 20 centimeters onto 180 grit sandpaper.If a glass-based article survived the drop from one height (e.g., 20cm), the mobile phone was dropped again from a greater height (e.g., 30cm, 40 cm, 50 cm, etc.) up to a height of 225 cm. The survivingglass-based articles were then dropped onto 30 grit sandpaper (in thesame phone devices). The height at which the glass-based article failedon both 180 grit sandpaper and 30 grit sandpaper is plotted in FIG. 13.As shown in FIG. 13, all but two glass-based articles of Example 2Asurvived being dropped onto 180 grit sandpaper up to heights of about225 cm (providing an average survival drop height of about 216 cm). Theaverage survival drop height onto 30 grit sandpaper was 66 cm, with somesurviving over 100 cm drop heights.

The glass based articles according to Example 2A exhibited a dielectricconstant of about 6.9 to about 7.05 over a frequency range from about480 mHz to about 3000 mHz. The glass-based articles according to Example2A exhibited a dielectric loss tangent in the range from about 0.012 toabout 0.015 over a frequency range from about 480 mHz to about 3000 mHz.

The refractive index of the glass-based articles according to Example 2Ais in the range from about 1.49 to about 1.518 over a range from about380 nm to about 1550 nm, and from about 1.497 to about 1.518 over awavelength range from about 380 nm to about 800 nm.

The glass-based articles according to Example 2A were subjected tovarious chemical treatments as shown in Table 5. The chemical durabilityof the glass-based articles was compared to Comparative Examples 2B, 2Cand 2D. Comparative Example 2B was a glass substrate having a nominalcomposition of 64.3 mol % SiO₂, 7.02 mol % B₂O₃, 14 mol % Al₂O₃, 14 mol% Na₂O, 0.5 mol % K₂O, 0.03 mol % Fe₂O₃, and 0.1 mol % SnO₂. ComparativeExample 2C was a glass substrate having a nominal composition of 64.75mol % SiO₂, 5 mol % B₂O₃, 14 mol % Al₂O₃, 13.75 mol % Na₂O, 2.4 mol %MgO, and 0.08 mol % SnO₂. Comparative Example 2D included a glasssubstrate having a nominal composition of 57.5 mol % SiO₂, 16.5 mol %Al₂O₃, 16.71 mol % Na₂O, 2.8 mol % MgO, 0.05 mol % SnO₂ and 6.5 mol %P₂O₅.

TABLE 5 Chemical durability of Example 2A and Comparative Examples 2B,2C, and 2D. Weight loss (mg/cm2) Chemical Comparative ComparativeComparative Treatment Example 2B Example 2C Example 2D Example 2A 5% w/wHCl, 29.3 6.7 50 5.77 95° C., 24 hours 5% w/w 2.8 2.4 5.8 2.68 NaOH, 95°C., 6 hours 10% HF, 20.8 18.1 37.4 24.03 room temperature, 20 minutes10% 2 2.7 3.2 0.98 ammonium bifluoride (ABF), room temperature, 20minutes

Example 3

Example 3A included glass substrates having the same composition asExample 1 and a thickness of 0.8 mm. Comparative Example 3B includedglass substrates having the same composition as Comparative Example 2Dand a thickness of 0.8 mm. The glass substrates of Example 3A werechemically strengthened in a single step using a single bath, asdescribed in Table 6. The glass substrates of Comparative Example 3B wasion exchanged in a two-step process, as described in Table 6.

TABLE 6 Ion exchange conditions for Example 3A and Comparative Example3B. Comparative Example 3A Example 3B 1^(st) Step Molten salt bath 49%NaNO3/ 49% NaNO3/51% composition 51% KNO3 KNO3 Bath Temperature 380° C.460° C. Immersion time 3.75 hours 14 hours 2^(nd) Step Molten salt bath— 99.5% KNO3/ composition 0.5% NaNO3 Bath Temperature — 390° C.Immersion time — 0.25 hours Properties of Surface CS 500 MPa 825 MParesulting Potassium DOL 12 micrometers 10 micrometers glass articleStress at potassium 160 MPa 220 MPa DOL DOC 150 micrometers 100micrometers

The glass-based articles according to Example 3A and Comparative Example3B were retrofitted onto identical mobile phone devices. The phonedevices were dropped from incremental heights starting at 20 centimetersonto 30 grit sandpaper. The height at which the glass-based articlefailed on 30 grit sandpaper is plotted in FIG. 14. As shown in FIG. 14,the glass-based articles of Example 3A exhibited an average survivaldrop height that is more than two times (i.e., 91 cm) the averagesurvival drop height of Comparative Example 3B (i.e., 38 cm).

Glass-based articles according to Example 3A and Comparative Example 3Bwere subjected to AROR testing, as described herein, using a load orpressure of 25 psi. The glass-based substrates of Example 3A exhibitedan average load to failure of about 30 kgf, while the glass-basedsubstrates of Comparative Example 3B exhibited an average load tofailure of about 27 kgf, as shown in FIG. 15. When the abrasion load orpressure was increased to 45 psi, the difference in average load tofailure for Example 3A and Comparative Example 3B increased.Specifically, under a 45 psi load or pressure, Example 3A exhibited anaverage load to failure of about 25.9 kgf, while Comparative Example 3Bexhibited an average load to failure of about 19.6 kgf, as shown in FIG.16.

Example 4

Glass substrates having a nominal composition of 57.5 mol % SiO₂, 16.5mol % Al₂O₃, 16.7 mol % Na₂O, 2.5 mol % MgO, and 6.5 mol % P₂O₅, andhaving a thicknesses of about 0.4 mm, 0.55 mm, or 1 mm were subjected tochemical strengthening. The thicknesses and conditions of chemicalstrengthening are shown in Table 7.

TABLE 7 Thickness and chemical strengthening conditions for Examples4A-4D. Ex. Thickness Bath Composition Bath Temperature 4A  0.4 mm 80%KNO3, 20% 430° C. NaNO3 4B 0.55 mm 80% KNO₃, 20% 430° C. NaNO₃ 4C 0.55mm 90% KNO₃, 10% 430° C. NaNO₃ 4D  1.0 mm 70% KNO₃, 30% 430° C. NaNO₃

Example 4A was immersed in a molten salt bath, as indicted in Table 7,for 4 hours, 8 hours, 16 hours, 32 hours, 64 hours and 128 hours(Examples 4A-1 through 4A-6). Example 4B was immersed in a molten saltbath, as indicated in Table 7, for 4 hours, 8 hours, 16 hours, 32 hours,64 hours and 128 hours (Examples 4B-1 through 4B-6). Example 4C wasimmersed in a molten salt bath, as indicated in Table 7, for 1 hour, 2hours, 4 hours, 8 hours, 16 hours and 32 hours (Examples 4C-1 through4C-6). Example 4D was immersed in a molten salt bath, as indicated inTable 7, for 4 hours, 8 hours, 16 hours, 32 hours, 64 hours and 128hours (Examples 4D-1 through 4D-6). The stress profiles of Examples 4A-1through 4A-6, 4B-1 through 4B-6, 6C-1 through 4C-6, and 4D-1 through4D-6 are shown in FIGS. 17, 19, 21 and 23, respectively. In FIGS. 17,19, 21 and 23, the depth or thickness of the glass articles is plottedon the x-axis and stress is plotted on the y-axis. The positive stressvalues are CT values and the negative stress values are the CS values.

The CT and DOC values as a function of time immersed in the molten saltbath for Examples 4A-1 through 4A-6, Examples 4B-1 through 4B-6,Examples 4C-1 through 4C-6 and 4D-1 through 4D-6, are shown in FIGS. 18,20, 22, and 24, respectively.

Example 5

Glass substrates having a nominal composition as shown in Table 8 andhaving a thicknesses of about 0.8 mm each were subjected to chemicalstrengthening in a molten salt bath including a mixture of NaNO₃ andNaSO₄ and a temperature of 500° C. for 15 minutes (Comparative Example8A) and for 16 hours (Example 8B).

TABLE 8 Composition of the glass substrate of Example 5, prior tochemical strengthening. Example =

Oxide [mole %] 5 SiO₂ 69.2 Al₂O₃ 12.6 B₂O₃ 1.8 Li₂O 7.7 Na₂O 0.4 MgO 2.9ZnO 1.7 TiO₂ 3.5 SnO₂ 0.1$\frac{\left\lbrack {{{Li}_{2}O} + {{Na}_{2}O} + {MgO} + {ZnO} + {K_{2}O}} \right\rbrack}{\left\lbrack {{{Al}_{2}O_{3}} + {B_{2}O_{3}}} \right\rbrack}$$\frac{12.7}{14.4} = 0.88$$\frac{\left\lbrack {{TiO}_{2} + {SnO}_{2}} \right\rbrack}{\left\lbrack {{SiO}_{2} + {B_{2}O_{3}}} \right\rbrack}$$\frac{3.6}{71} = 0.051$

The stress profile of the glass-based articles of Examples 5A and 5B areshown in FIG. 25. A shown in FIG. 25, Comparative Example 5A exhibited aknown stress profile, whereas, Example 5B showed a stress profileaccording to one or more embodiments of this disclosure. The storedtensile energy of the glass-based articles of Examples 5A and 5B wascalculated from the measured SCALP stress profile data and usingequation (2) above. The calculated stored tensile energy is plotted as afunction of measured CT (MPa), as shown in FIG. 26.

As shown in FIG. 26, Comparative 5A exhibited much greater storedtensile energy values for a given CT value than Example 5B (for the sameCT value). In this figure, CT is the maximum CT in the sample.Specifically, at a CT of about 55 MPa, Comparative Example 5A exhibiteda stored tensile energy of about 6.5 J/m², whereas Example 5B exhibiteda stored tensile energy of about 3.5 J/m². Comparative Example 5A andExample 5B were fractured and Example 5B fractured into fewer piecesthan Comparative Example 5A, which fractured into a significantlygreater number of pieces. Accordingly, without being bound by theory, itis believed that controlling the stored tensile energy may provide a wayto control or predict fragmentation patterns or the number of fragmentsthat result from fracture. In these examples, the CT was varied bykeeping a sample in the ion exchange bath for a longer period of timewhile using the same bath temperature and composition. In FIG. 26, thepoint 0,0 was not experimental, but is would one of ordinary skill inthe art would expect to be the case, i.e., when there is 0 CT, therewill be 0 stored tensile energy.

Glass substrates having a nominal composition as shown in Table 8 andhaving a thicknesses of about 1 mm each were subjected to chemicalstrengthening in a molten salt bath including NaNO₃ and a temperature of430° C. for 4 hours (Comparative Example 5C) and for 61.5 hours (Example5D). Comparative Example 5C exhibited a known stress profile, whereas,Example 5D showed a stress profile according to one or more embodimentsof this disclosure. The stored tensile energy of Examples 5C and 5D wascalculated using the same method used with Examples 5A-5B and plotted asa function of measured CT (MPa), as shown in FIG. 27.

As shown in FIG. 27, Comparative 5C exhibited much greater storedtensile energy values for a given CT (again, as with FIG. 27, these aremaximum CT values, and again the values were varied by using the sameion exchange bath temperature and composition, but with longer periodsof time) value than Example 5D (for the same CT value). ComparativeExample 5C and Example 5D were fractured and Example 5D fractured intofewer pieces than Comparative Example 5C, which fractured into asignificantly greater number of pieces.

Example 6

Table 9 lists exemplary compositions (Examples 6A-6J) of the glasssubstrates described herein. Table 10 lists selected physical propertiesdetermined for the examples listed in Table 9. The physical propertieslisted in Table 10 include: density; CTE; strain, anneal and softeningpoints; liquidus temperature; liquidus viscosity; Young's modulus;refractive index, and stress optical coefficient.

TABLE 9 Examples of alkali aluminosilicate glass compositions.Composition (mol %) Ex. 6A Ex. 6B Ex. 6C Ex. 6D Ex. 6E Ex. 6F Ex. 6GAl₂O₃ 16.67 16.73 16.70 16.73 16.17 16.13 15.73 B₂O₃ Cs₂O 0.46 Li₂O 7.467.41 7.30 7.42 7.45 7.54 7.45 Na₂O 8.75 8.28 7.77 7.85 8.30 7.76 8.77P₂O₅ 3.46 3.95 3.94 3.92 3.45 3.94 3.38 SiO₂ 63.62 63.58 64.24 63.5663.61 63.61 63.71 SnO₂ 0.05 0.05 0.05 0.05 0.05 0.05 ZnO 0.98 0.97 0.96R₂O 16.21 15.69 15.07 15.27 15.75 15.30 16.22 B₂O₃ + P₂O₅ + 83.74 84.2684.88 84.22 83.23 83.68 82.82 SiO₂ + Al₂O₃ Composition (mol %) Ex. 6HEx. 6I Ex. 6J Al₂O₃ 15.65 16.68 16.66 B₂O₃ Cs₂O Li₂O 7.47 9.99 12.38Na₂O 8.27 7.32 4.84 P₂O₅ 3.91 2.45 2.44 SiO₂ 63.67 63.50 63.63 SnO₂ 0.050.05 0.05 ZnO 0.98 R2O 15.74 17.31 17.22 B₂O₃ + P₂O₅ + 83.23 82.64 82.73SiO₂ + Al₂O₃

TABLE 10 Selected physical properties of the glasses listed in Table 9.Ex. 6A Ex. 6B Ex. 6C Ex. 6D Ex. 6E Ex. 6F Ex. 6G Fulchers A −3.933−3.681 −3.994 −4.132 −4.049 −3.657 −4.147 Fulchers B 10000.7 9453.710199.7 10556.7 10414.5 9531.9 10785.5 Fulchers To 50.4 85.5 41.3 22.6−0.8 50.1 −38.5 200 P Temperature (° C.) 1655 1666 1662 1664 1639 16501634 35000 P Temperature (° C.) 1230 1235 1236 1239 1211 1212 1202200000 P Temperature (° C.) 1133 1138 1139 1142 1113 1114 1103 Density(g/cm³) 2.396 2.389 2.389 2.413 2.413 2.406 2.415 CTE 25-300° C. (ppm/°C.) 73.9 71.7 72.5 72.8 71.5 69 74.7 Strain pt. (° C.) 606 605 604 605587 589 578 Anneal pt. (° C.) 661 662 661 661 642 644 631 Softening pt.(° C.) 926.4 931.7 930.3 935.1 908.6 912.3 898.4 Liquidus temperature (°C.) 1080 1095 1090 1095 1080 1100 1055 Liquidus viscosity (P) 602823482764 539563 515222 386294 264159 520335 Stress optical coefficient30.04 30.43 30.43 30.4 30.51 3.083 30.34 (nm/min/MPa) Refractive indexat 589.3 nm 1.5016 1.5003 1.5003 1.5010 1.5037 1.5021 1.5035 Young'smodulus (GPa) 75.84 75.57 75.70 75.15 76.67 75.77 76.12 Ex. 6H Ex. 6IEx. 6J Fulchers A −3.649 −3.231 −2.918 Fulchers B 9623.9 8275.1 7331.7Fulchers To 33.9 126.8 188.3 200 P Temperature (° C.) 1651 1623 159335000 P Temperature (° C.) 1209 1191 1171 200000 P Temperature (° C.)1109 1097 1080 Density (g/cm3) 2.408 2.401 2.394 CTE 25-300° C. (ppm/°C.) 71.7 74.5 70.4 Strain pt. (° C.) 579 607 607 Anneal pt. (° C.) 633656 656 Softening pt. (° C.) 898.7 900.7 900 Liquidus temperature (° C.)1090 1180 1265 Liquidus viscosity (P) 290856 42277 7788 Stress opticalcoefficient 3.028 2.937 2.926 (nm/mm/MPa) Refractive index at 589.3 nm1.5022 1.5071 1.5099 Young's modulus (GPa) 75.84 78.60 79.91

Examples 6A-6H were formed into glass articles (having a sheet form andspecific thickness) and then chemically strengthened by immersing in amolten salt bath having a specific temperature, for a specifiedduration. Table 11 shows the thickness of each glass article, thechemical strengthening conditions, and the measured maximum CT and DOCvalues of the resulting strengthened glass article.

TABLE 11 Chemical strengthening conditions and resulting attributes ofthe glass articles. Ex. 6A Ex. 6B Ex. 6C Ex. 6D Immersion in a moltensalt bath of 100% NaNO₃ having a temperature of 390° C. for 4 hoursThickness 1.07 1.11 1.11 1.05 (mm) Maximum 81 76 72 74 CT (MPa) DOC as a0.19 0.19 0.19 0.17 fraction of thickness Immersion in a molten saltbath of 100% NaNO₃ having a temperature of 390° C. for 6 hours Thickness1.08 1.1 1.12 1.04 (mm) Maximum 89 80 87 86 CT (MPa) DOC as a 0.18 0.20.19 0.19 fraction of thickness Immersion in a molten salt bath of 100%NaNO₃ having a temperature of 390° C. for 8 hours Thickness 1.07 1.11.11 1.03 (mm) Maximum 88 83 84 87 CT (MPa) DOC as a 0.19 0.2 0.2 0.17fraction of thickness Ex. 6E Ex. 6F Ex. 6G Ex. 6H Immersion in a moltensalt bath of 100% NaNO₃ having a temperature of 390° C. for 4 hoursThickness 1.05 1.02 1.09 1.09 (mm) Maximum 81 82 77 73 CT (MPa) DOC as a0.17 0.16 0.17 0.18 fraction of thickness Immersion in a molten saltbath of 100% NaNO₃ having a temperature of 390° C. for 6 hours Thickness1.08 1.03 1.07 1.1 (mm) Maximum 81 82 85 85 CT (MPa) DOC as a 0.2 0.20.19 0.2 fraction of thickness Immersion in a molten salt bath of 100%NaNO₃ having a temperature of 390° C. for 8 hours Thickness 1.06 1.041.09 1.1 (mm) Maximum 84 87 84 83 CT (MPa) DOC as a 0.18 0.18 0.2 0.19fraction of thickness

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention. For example, the various features canbe combined according to the following exemplary embodiments.

Embodiment 1

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) (mm);

a concentration of a metal oxide that is both non-zero and varies alonga thickness range from about 0·t to about 0.3·t; and

a central tension (CT) region comprising a maximum CT (MPa) of less thanabout 71.5/√(t),

wherein, when the glass-based article is fractured, the glass-basedarticle fractures into 2 or less fragments/inch², when tested on asample size of 5 cm by 5 cm (2 inch by 2 inch) square.

Embodiment 2

The glass-based article of embodiment 1, wherein the concentration ofthe metal oxide is non-zero and varies along the entire thickness.

Embodiment 3

The glass-based article of any one of the preceding embodiments,comprising a surface compressive stress (CS) of about 300 MPa orgreater.

Embodiment 4

The glass-based article of embodiment 3, wherein the surface CS is about400 MPa or greater.

Embodiment 5

The glass-based article of any one of the preceding embodiments, whereinthe CT region comprises the metal oxide concentration gradient.

Embodiment 6

A glass-based article of any one of the preceding embodiments,comprising:

a first metal oxide concentration and a second metal oxideconcentration,

wherein the first metal oxide concentration varies in a range from about15 mol % to about 0 mol % as thickness varies over a first range fromabout 0·t to about 0.5·t, and

wherein the second metal oxide concentration varies in a range fromabout 0 mol % to about 10 mol % as thickness varies over a second rangefrom about 0 micrometers to about 25 micrometers from at least one ofthe first surface and the second surface.

Embodiment 7

The glass-based article of embodiment 6, comprising a third metal oxide.

Embodiment 8

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t); and

a concentration of a metal oxide that is both non-zero and varies alonga thickness range from about 0·t to about 0.3·t;

a surface compressive stress of about 200 MPa or greater; and

a CT region having a maximum CT less than about 71.5/√(t).

Embodiment 9

The glass-based article of embodiment 8, wherein the thickness range ofthe metal oxide concentration is from about 0·t to about 0.4·t.

Embodiment 10

The glass-based article of embodiment 8 or embodiment 9, wherein thethickness range of the metal oxide concentration is from about 0·t toabout 0.45·t.

Embodiment 11

The glass-based article of any one of embodiments 1-10, wherein amonovalent ion of the metal oxide generates a stress along the thicknessrange.

Embodiment 12

The glass-based article of embodiment 11, wherein the monovalent ion ofthe metal oxide has a largest ionic diameter of all of the monovalentions of the metal oxides in the glass-based article.

Embodiment 13

The glass-based article of any one of embodiments 1-12, wherein theconcentration of the metal oxide decreases from the first surface to avalue at a point between the first surface and the second surface andincreases from the value to the second surface.

Embodiment 14

The glass-based article of any one of embodiments 1-13, wherein theglass-based article comprises a sodium or potassium ion diffusivity ofabout 450 μm²/hour or greater at about 460° C. and a DOC greater thanabout 0.15·t, and wherein the surface CS is 1.5 times the maximum CT orgreater.

Embodiment 15

The glass-based article of any one of embodiments 8-14, wherein theabsolute value of surface CS is greater than the absolute value ofmaximum CT.

Embodiment 16

The glass-based article of any one of embodiments 8-15, wherein thesurface CS is about 300 MPa or greater and a thickness of about 2millimeters or less.

Embodiment 17

The glass-based article of any one of embodiments 8-16, wherein the CTregion comprises the metal oxide that is both non-zero and varies alonga thickness range from about 0·t to about 0.3·t.

Embodiment 18

The glass-based article of any one of embodiments 1-17, wherein theratio of maximum CT to absolute value of surface CS is in the range fromabout 0.1 to about 0.2.

Embodiment 19

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) of about less than about 3 millimeters; and

a stress profile extending along the thickness,

wherein all points of the stress profile between a thickness range fromabout 0·t up to 0.3·t and from greater than about 0.7·t to t, comprise atangent with a slope having an absolute value that is greater than about0.1 MPa/micrometer,

wherein the stress profile comprises a maximum CS, a DOC and a maximumCT of less than about 71.5/√(t) (MPa), wherein the ratio of maximum CTto absolute value of maximum CS is in the range from about 0.01 to about0.2 and wherein the DOC is about 0.1·t or greater, and

wherein, when the glass-based article is fractured, the glass-basedarticle fractures into 2 or less fragments/inch², when tested on asample size of 5 cm by 5 cm (2 inch by 2 inch) square.

Embodiment 20

The glass-based article of any one of embodiments 1-7 or embodiment 19,comprising a surface CS of about 200 MPa or greater and a chemical depthof layer of about 0.4·t or greater.

Embodiment 21

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) (mm);

a concentration of a metal oxide that is both non-zero and varies alonga thickness range from about 0·t to about 0.3·t; and

a central tension (CT) region comprising a maximum CT (MPa) of less thanabout 71.5/√(t),

wherein the article exhibits at least one of:

-   -   (i) a threshold failure impact force greater than 500 Newtons        when the article is bent to impart a tensile stress of 100 MPa;        and    -   (ii) a retained strength of 125 or more MPa after being impacted        by an impact force of 800 N when the article is bent to impart a        tensile stress of 100 MPa.

Embodiment 22

The glass-based article of embodiment 21, wherein the glass-basedarticle has a surface compressive stress of greater than about 200 MPa.

Embodiment 23

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) of about less than about 3 millimeters; and

a stress profile extending along the thickness,

wherein all points of the stress profile between a thickness range fromabout 0·t up to 0.3·t and from greater than about 0.7·t to t, comprise atangent with a slope having an absolute value that is greater than about0.1 MPa/micrometer,

wherein the stress profile comprises a maximum CS, a DOC and a maximumCT of less than about 71.5/√(t) (MPa), wherein the ratio of maximum CTto absolute value of maximum CS is in the range from about 0.01 to about0.2 and wherein the DOC is about 0.1·t or greater, and

wherein the article exhibits at least one of:

-   -   (i) a threshold failure impact force greater than 500 Newtons        when the article is bent to impart a tensile stress of 100 MPa;        and    -   (ii) a retained strength of 125 or more MPa after being impacted        by an impact force of 800 N when the article is bent to impart a        tensile stress of 100 MPa.

Embodiment 24

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) (mm); and

a metal oxide that forms a concentration gradient,

wherein the concentration of the metal oxide decreases from the firstsurface to a value at a point between the first surface and the secondsurface and increases from the value to the second surface,

wherein the concentration of the metal oxide at the point is non-zero,and

wherein the glass-based article comprises a stored tensile energy ofabout greater than 0 J/m² to less than 25 J/m² and a Young's modulus ofless than about 80 GPa.

Embodiment 25

The glass-based article of any one of embodiments 1-18, or 24, whereinthe concentration of the metal oxide is about 0.05 mol % or greaterthroughout the thickness.

Embodiment 26

The glass-based article of any one of embodiments 1-18, 24, or 25,wherein the concentration of the metal oxide at the first surface isabout 1.5 or more times greater than the concentration of the metaloxides at a depth equal to about 0.5·t.

Embodiment 27

The glass-based article of any one of embodiments 1-18, 20, or 24-26,wherein the total concentration of the metal oxide is in the range fromabout 1 mol % to about 15 mol %.

Embodiment 28

The glass-based article of any one of embodiments 1-18, 20, or 24-27,wherein the metal oxide comprises any one or more of Li₂O, Na₂O, K₂O,Rb₂O, and Cs₂O.

Embodiment 29

The glass-based article of any one of embodiments 1-18, 20, or 24-28,comprising a CS layer extending from the first surface to a DOC, whereinthe DOC is about 0.1·t or greater.

Embodiment 30

The glass-based article of any one of embodiments 19, 20, or 24-29,wherein the CT region comprises a maximum CT and the ratio of maximum CTto absolute value of surface CS is in the range from about 0.01 to about0.2.

Embodiment 31

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) of about less than about 3 millimeter; and

a stress profile extending along the thickness,

wherein the stress profile at all points between a thickness range fromabout 0t up to 0.3t and from greater than about 0.7·t to t, comprise alocal gradient having an absolute value that is greater than about 0.1MPa/micrometer,

wherein the stress profile comprises a maximum CS, a DOC and a maximumCT, wherein the ratio of maximum CT to absolute value of maximum CS isin the range from about 0.01 to about 0.2 and wherein the DOC is about0.1·t or greater, and

wherein the glass-based article comprises a stored tensile energy ofabout greater than 0 J/m² to less than 25 J/m² and a Young's modulus ofless than about 80 GPa.

Embodiment 32

The glass-based article of embodiment 31, comprising a non-zeroconcentration of a metal oxide that continuously varies along the entirethickness.

Embodiment 33

The glass-based article of embodiment 31 or embodiment 32, comprising anon-zero concentration of a metal oxide that continuously varies along athickness segment of about 10 micrometers.

Embodiment 34

The glass-based article of any one of embodiments 19, 20, 25, or 31-33,wherein the maximum CS comprises about 300 MPa or greater.

Embodiment 35

The glass-based article of any one of embodiments 8-18, or 31-34,comprising a chemical depth of layer of about 0.4·t or greater.

Embodiment 36

The glass-based article of any one of embodiments 19, 20, 24-29, 31-35,comprising a CT region, wherein the CT region comprises the metal oxideconcentration gradient.

Embodiment 37

The glass-based article of any one of embodiments 24-36, wherein themaximum CT is less than about 71.5/√(t) (MPa).

Embodiment 38

A glass-based article comprising:

a stress profile including a CS region and a CT region, wherein the CTregion is approximated by the equationStress(x)=MaxT−(((CT_(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(n)),

wherein MaxT is a maximum tension value and is a positive value in unitsof MPa,

wherein CT_(n) is the tension value at n, CT_(n) is less than or equalto MaxT, and is a positive value in units of MPa,

wherein x is position along the thickness (t) in micrometers, and x=0 ata surface of the glass-based article, and

wherein n is in the range from 1.5 to 5.

Embodiment 39

The glass-based article of embodiment 38, wherein n is in the range from1.5 to 2.

Embodiment 40

The glass-based article of embodiment 38 or 39, wherein the CT regioncomprises a maximum CT value in the range from about 50 MPa to about 250MPa and the maximum CT value is at a depth in the range from about 0.4tto about 0.6t.

Embodiment 41

The glass-based article of any one of embodiments 38-40, wherein, for athickness in the range from about Otto about 0.1t, the stress profilecomprises a slope whose magnitude in absolute value is in the range fromabout 20 MPa/micron to about 200 MPa/micron.

Embodiment 42

The glass-based article of embodiment any one of embodiments 38-41,wherein the stress profile is approximated by a combination of aplurality of error functions as measured from 0.5t to the surface.

Embodiment 43

A glass-based article comprising:

a stress profile including a CS region and a CT region, wherein the CTregion is approximated by the equationStress(x)=MaxT−(((CT_(n)·(n+1))/0.5^(n))·|(x/t)−0.5|^(n)),

wherein MaxT is a maximum tension value and is a positive value in unitsof MPa,

wherein CT_(n) is the tension value at n, CT_(n) is less than or equalto MaxT, and is a positive value in units of MPa,

wherein x is position along the thickness (t) in micrometers, and x=0 ata surface of the glass-based article,

wherein n is in the range from 1.5 to 5, and

wherein the article exhibits at least one of:

-   -   (i) a threshold failure impact force greater than 500 Newtons        when the article is bent to impart a tensile stress of 100 MPa;        and    -   (ii) a retained strength of 125 or more MPa after being impacted        by an impact force of 800 N when the article is bent to impart a        tensile stress of 100 MPa.

Embodiment 44

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t) (mm); and

a metal oxide that forms a concentration gradient,

wherein the concentration of the metal oxide decreases from the firstsurface to a value at a point between the first surface and the secondsurface and increases from the value to the second surface,

wherein the concentration of the metal oxide at the point is non-zero,and

wherein the article exhibits at least one of:

-   -   (i) a threshold failure impact force greater than 500 Newtons        when the article is bent to impart a tensile stress of 100 MPa;        and    -   (ii) a retained strength of 125 or more MPa after being impacted        by an impact force of 800 N when the article is bent to impart a        tensile stress of 100 MPa.

Embodiment 45

The glass-based article of any one of embodiments 21-23, 43, or 44,wherein the article exhibits a threshold failure impact force greaterthan 600 Newtons.

Embodiment 46

The glass-based article of any one of embodiments 21-23, 44 or 44,wherein the article exhibits a threshold failure impact force greaterthan 700 Newtons.

Embodiment 47

The glass-based article of any one of embodiments 21-23, 43, or 44,wherein the article exhibits a threshold failure impact force greaterthan 800 Newtons.

Embodiment 48

The glass-based article of any one of embodiments 21-23, 43 or 44,wherein the article exhibits a retained strength of 150 or more MPa.

Embodiment 49

The glass-based article of any one of embodiments 21-23, 43 or 44,wherein the article exhibits a retained strength of 200 or more MPa.

Embodiment 50

The glass-based article of any one of the preceding embodiments, whereint comprises about 3 millimeters or less.

Embodiment 51

The glass-based article of any one of the preceding embodiments, theglass-based article is amorphous.

Embodiment 52

The glass-based article of any one of the preceding embodiments, theglass-based article is crystalline.

Embodiment 53

The glass-based article of any one of the preceding embodiments, furtherexhibiting a transmittance of about 88% or greater over a wavelength inthe range from about 380 nm to about 780 nm.

Embodiment 54

The glass-based article of any one of the preceding embodiments, furtherexhibiting CIELAB color space coordinates, under a CIE illuminant F02,of L* values of about 88 and greater, a* values in the range from about−3 to about +3, and b* values in the range from about −6 to about +6.

Embodiment 55

The glass-based article of any one of the preceding embodiments, whereinthe glass-based article comprises a fracture toughness (K_(1C)) of about0.65 MPa·m^(1/2) or greater.

Embodiment 56

The glass-based article of any one of the preceding embodiments,comprising a Young's modulus of less than 80 GPa.

Embodiment 57

The glass-based article of any one of the preceding embodiments, whereint comprises about 1 millimeters or less.

Embodiment 58

The glass-based article of any one of the preceding embodiments,comprising a liquidus viscosity of about 100 kP or greater.

Embodiment 59

The glass-based article of any one of the preceding embodiments,comprising any one or more of:

a composition comprising a combined amount of Al₂O₃ and Na₂O of greaterthan about 17 mol %,

a composition comprising greater than about 4 mol % Na₂O,

a composition substantially free of B₂O₃, ZnO, or both B₂O₃ and ZnO, and

a composition comprising a non-zero amount of P₂O₅.

Embodiment 60

A device comprising:

a housing having front, back, and side surfaces;

electrical components that are at least partially inside the housing;

a display at or adjacent to the front surface of the housing; and

a cover substrate disposed over the display, wherein the cover substratecomprises the glass-based article of any one of the precedingembodiments.

What is claimed is:
 1. A glass-based article comprising: a first surfaceand a second surface opposing the first surface defining a thickness (t)(mm); a concentration of a metal oxide that is both non-zero and variesalong a thickness range from about 0·t to about 0.3·t; and a centraltension (CT) region comprising a maximum CT (MPa) of less than about71.5/√(t), wherein, when the glass-based article is fractured, theglass-based article fractures into 2 or less fragments/inch², whentested on a sample size of 2 inch by 2 inch square.
 2. The glass-basedarticle of claim 1, wherein the concentration of the metal oxide isnon-zero and varies along the entire thickness.
 3. A glass-based articleof claim 1, comprising: a first metal oxide concentration and a secondmetal oxide concentration, wherein the first metal oxide concentrationvaries in a range from about 15 mol % to about 0 mol % as thicknessvaries over a first range from about 0·t to about 0.5·t, and wherein thesecond metal oxide concentration varies in a range from about 0 mol % toabout 10 mol % as thickness varies over a second range from about 0micrometers to about 25 micrometers from at least one of the firstsurface and the second surface.
 4. A glass-based article comprising: afirst surface and a second surface opposing the first surface defining athickness (t); and a concentration of a metal oxide that is bothnon-zero and varies along a thickness range from about 0·t to about0.3·t; a surface compressive stress of about 200 MPa or greater; and aCT region having a maximum CT less than about 71.5/√(t).
 5. Theglass-based article of claim 1, wherein a monovalent ion of the metaloxide generates a stress along the thickness range, and wherein themonovalent ion of the metal oxide has a largest ionic diameter of all ofthe monovalent ions of the metal oxides in the glass-based article. 6.The glass-based article of claim 1, wherein the concentration of themetal oxide decreases from the first surface to a value at a pointbetween the first surface and the second surface and increases from thevalue to the second surface.
 7. The glass-based article of claim 1,wherein the glass-based article comprises a sodium or potassium iondiffusivity of about 450 μm²/hour or greater at about 460° C. and a DOCgreater than about 0.15·t, and wherein the surface CS is 1.5 times themaximum CT or greater.
 8. The glass-based article of claim 1, whereinthe ratio of maximum CT to absolute value of surface CS is in the rangefrom about 0.1 to about 0.2.
 9. The glass-based article or claim 1,comprising: the thickness (t) is about 3 millimeters or less; and astress profile extending along the thickness, wherein all points of thestress profile between a thickness range from about 0·t up to 0.3·t andfrom greater than about 0.7·t to t, comprise a tangent with a slopehaving an absolute value that is greater than about 0.1 MPa/micrometer,and wherein the stress profile comprises a maximum CS, a DOC and the CTregion, wherein the ratio of maximum CT to absolute value of maximum CSis in the range from about 0.01 to about 0.2 and wherein the DOC isabout 0.1·t or greater.
 10. The glass-based article of claim 4, whereinthe article exhibits at least one of: (i) a threshold failure impactforce greater than 500 Newtons when the article is bent to impart atensile stress of 100 MPa; and (ii) a retained strength of 125 MPa ormore after being impacted by an impact force of 800 N when the articleis bent to impart a tensile stress of 100 MPa.
 11. The glass-basedarticle of claim 9, wherein the article exhibits at least one of: (i) athreshold failure impact force greater than 500 Newtons when the articleis bent to impart a tensile stress of 100 MPa; and (ii) a retainedstrength of 125 or more MPa after being impacted by an impact force of800 N when the article is bent to impart a tensile stress of 100 MPa.12. The glass-based article of claim 1, further exhibiting atransmittance of about 88% or greater over a wavelength in the rangefrom about 380 nm to about 780 nm.
 13. The glass-based article of claim1, further exhibiting CIELAB color space coordinates, under a CIEilluminant F02, of L* values of about 88 and greater, a* values in therange from about −3 to about +3, and b* values in the range from about−6 to about +6.
 14. The glass-based article of claim 1, wherein theglass-based article comprises a fracture toughness (K_(1C)) of about0.65 MPa·m^(1/2) or greater.
 15. The glass-based article of claim 1,comprising a Young's modulus of less than 80 GPa.
 16. The glass-basedarticle of claim 1, wherein t comprises about 1 millimeters or less. 17.The glass-based article of claim 1, comprising a liquidus viscosity ofabout 100 kP or greater.
 18. The glass-based article of claim 1,comprising any one or more of: a composition comprising a combinedamount of Al₂O₃ and Na₂O of greater than about 17 mol %, a compositioncomprising greater than about 4 mol % Na₂O, a composition substantiallyfree of B₂O₃, ZnO, or both B₂O₃ and ZnO, and a composition comprising anon-zero amount of P₂O₅.
 19. A device comprising: a housing havingfront, back, and side surfaces; electrical components that are at leastpartially inside the housing; a display at or adjacent to the frontsurface of the housing; and a cover substrate disposed over the display,wherein the cover substrate comprises the glass-based article of claim1.